4 


A  DICTIONARY  OF 
PHOTOGRAPHY 

TOR  THE 

Amateur  mb  ^xofmimid  yfyrtqpayfyer. 

E.   J.    WALL,  F.R.P.S., 

AUTHOR  OF  "CARBON  PRINTING." 

CONTAINING  CONCISE  AND  EXPLANATORY  ARTICLES, 
ILLUSTRATED  BY  MANY  SPECIALLY  PREPARED  DIAGRAMS. 

SIXTH  EDITION. 

MOSTLY  RE-  WRITTEN  AND  GREATLY  ENLARGED. 


NEW  YORK: 

GEORGE    I).  HURST 

PUBLISHER. 


DICTIONARY  OF  PHOTOGRAPHY. 


Aberration.  Unfortunately,  the  optician,  from  the  nature  of 
his  material  and  other  circumstances,  cannot  construct  lenses 
absolutely  perfect  and  free  from  error  or  aberration.  Aberration 
is  used  "  to  designate  the  unequal  deviation  of  rays  of  light  when 
refracted  by  a  lens,  by  which  they  are  prevented  from  uniting  to 
a  point " ;  it  is  generally  defined  as  meaning  errors  or  faults 
which  are  more  or  less  inseparable  from  an  otherwise  perfect 
instrument.  The  aberrations  to  which  photographic  lenses  are 
subject  arefive — viz.,  Astigmatism,  Chromatic  Aberration,  Spherical 
Aberration,  the  aberration  of  form  or  Curvature  of  the  Field  (q.v.), 
and  the  aberration  of  thickness  or  distortion  (q.v.y,  which  will 
be  treated  of  under  their  respective  headings. 

Absolute  Alcohol.    See  Alcohol. 

Accelerator.  A  term  applied  to  any  substance  which  is  used 
to  shorten  the  duration  of  development  and  to  obtain  the  impres- 
sion of  the  slightest  impact  of  actinic  light.  Thus,  in  alkaline 
pyro  development  the  alkali  is  the  accelerator,  and  with  ferrous 
oxalate,  hyposulphite  of  soda,  common  salt,  and  perchloride  of 
mercury  have  been  recommended.  A  few  drops  of  a  weak  solution 
of  hypo  have  a  wonderful  effect  in  bringing  up  detail  in  an 
instantaneous  negative.  Common  salt  has  also  a  beneficial 
effect,  especially  with  positive  bromide  papers,  bringing  up  the 
detail  evenly  and  gradually  before  the  shadows  can  become 
blocked.  The  addition  of  hypo  and  chloride  of  soda  to  ferrous 
oxalate  developer  is  stated  to  materially  shorten  the  time  of 
exposure,  but  it  is  doubtful  whether  the  action  is  not  rather 
limited  to  producing  a  visible  image  of  every  ray  of  light,  which 
may  not  be  the  case  with  ordinary  development.  See  also 
Development,  and  Developers. 

i  li 


Acc] 


DICTIONARY  OF  PHOTOGRAPHY. 


Accessories.   See  Portraiture. 

Acetate  of  Amyl.   See  Amyl  Acetate. 

Acetate  of  Copper.   See  Copper  Acetate. 

Acetate  of  Lead.   See  Lead  Acetate. 

Acetate  of  Silver.   See  Silver  Acetate. 

Acetate  of  Soda.   See  Sodium  Acetate. 

Acetates  are  salts  formed  by  the  combination  of  metals  with 
acetic  acid. 

Acetic  Acid  (Ger.,  Essigsiiure ;  Fr.,  Acide  Acetique ;  Ital. 
Acido  Aceticd).  Formula,  HC2H302 ;  molecular  weight,  60 ; 
synonym,  Purified  Pyroligneous  Acid.  Prepared  from  wood 
by  destructive  distillation  and  subsequent  purification.  There 
are  three  commercial  strengths. 

Glacial  Acetic  Acid  contains  99  per  cent,  of  acid  and  1  per 
cent,  of  water.  Its  specific  gravity  varies  from  1-065  to  I-°66. 
When  cooled  to  34°  F.  it  solidifies  into  a  mass  of  crystals,  and 
remains  solid  till  the  temperature  is  raised  to  480.  From  this 
property  is  derived  the  term  glacial.  Care  should  be  exercised 
in  handling  this,  as  it  is  a  powerful  escharotic;  if  any  should 
by  chance  be  spilt  upon  the  naked  skin,  an  alkali  should  be 
immediately  applied.  It  is,  of  course,  a  poison,  by  reason  of 
its  escharotic  properties — the  obvious  antidote  is  chalk,  lime, 
or  other  alkalies.  It  is  miscible  with  water  and  alcohol  in  all 
proportions.    It  is  a  solvent  of  pyroxyline. 

Acetic  Acid.  This  is  one-third  the  strength  of  the  glacial  acid, 
containing  about  33  per  cent,  of  real  acid.  It  can  be  conveniently 
prepared  from  the  stronger  acid  by  mixing  with  it  twice  its 
own  quantity  of  distilled  water.  It  is  sometimes  known  as 
"  Beaufoy's  Acetic  Acid."    Specific  gravity,  1*044. 

Dilute  Acetic  Acid.  Made  by  mixing  1  part  of  acetic  acid  and 
7  parts  of  distilled  water.  Specific  gravity,  1 -006.  It  contains  but 
3-63  per  cer.t.  of  acid.  The  impurities  in  the  acetic  acids  may 
be  either  sulphurous  acid  or  tarry  matter,  both  of  which  may  be 
detected  by  the  addition  of  a  few  drops  of  solution  of  nitrate  of 
silver.  A  white  precipitate  denotes  sulphurous  acid, -and  the 
darkening  of  the  solution  in  light  indicates  tarry  matter. 

2 


DICTIONARY  OF  PHOTOGRAPHY. 


[Act 


Their  uses  in  photography  are  limited  to  a  clearing  bath  for 
Bromide  Papers  (g.v.),  and  for  the  formation  of  salts  known  as 
acetates. 

Achromatic,  when  applied  to  a  lens,  signifies  that  it  has 
been  corrected  for  chromatic  aberration,  and  that  the  imager 
projected  by  it  are  unaccompanied  by  fringes  of  various  colours. 
The  correction  is  usually  effected  by  combining  two  glasses 
having  differing  refractive  powers,  as,  for  instance,  a  convex 
crown-glass  lens  with  a  concave  flint  glass,  or  by  enclosing  a 
flint  meniscus  between  two  concavo-convex.  There  are  several 
methods,  but  the  latter  is  the  usual  method  employed  for  the 
rapid  class  of  lenses  now  so  much  in  vogue  (see  Lens).  (For  the 
theory  involved  in  rendering  lenses  achromatic,  see  Decompo- 
sition of  Light.) 

Acids  may  be  defined  as  compounds  of  hydrogen  whose 
atom  or  atoms  of  hydrogen  are  replaceable  by  metals,  or  by 
radicals  having  metallic  characteristics,  and  the  compound 
resulting  from  such  substitution  is  termed  a  salt. 

Actinic  applies  to  that  portion  of  light  which  effects  chemical 
change,  in  distinction  to  those  portions  which  furnish  light  and 
heat.  The  actinic  portion  of  the  spectrum  may  be  said  to  be 
confined  to  the  ultra-violet,  violet,  indigo,  blue,  and  green  ;  not, 
as  might  be  supposed,  to  that  portion  which  appears  to  us  to  be 
the  most  powerful — viz.,  the  yellow.  But  the  division  is  entirely 
arbitrary,  as  it  depends  solely  upon  the  substance  exposed  as  to 
which  rays  are  actinic  or  non-actinic. 

Actinic  Focus  of  Lens.   See  Focus. 

Actinograph — Actinometer.  Any  instrument  which  mea- 
sures the  actinism  of  the  sun's  rays.  It  usually  consists  of 
sensitive  paper,  which  can  be  exposed  to  the  light  in  small 
portions  at  a  time ;  and  the  time  which  it  takes  to  darken  to  a 
standard  tint  will  be  found  to  bear  a  distinct  relation  to  the 
necessary  exposure  required  for  a  sensitive  film,  whether  upon 
glass  or  paper,  due  allowance  being  made  for  the  presence  of 
any  object  of  importance  near  the  foreground  of  picture.  An 
actinometer  can  be  made  by  any  amateur  by  soaking  a  strip  of 
gelatino-bromide  paper  in  a  2  per  cent,  solution  of  nitrite  of 

3 


Ada] 


DICTIONARY  OF  PHOTOGRAPHY. 


potash,  drying  the  same  in  the  dark.  When  dry  it  should  be 
rolled  up  small  and  placed  in  the  inside  of  a  box  which  is  light- 
tight,  and  from  which  the  paper  can  be  drawn  in  small  pieces 
to  allow  of  its  exposure  to  light  and  comparison  with  a  standard 
tint,  which  can  be  obtained  by  exposing  a  plate  on  a  subject  the 
exposure  of  which  is  known,  and  at  the  same  time  exposing  the 
actinometer  and  noting  the  time  of  the  darkening  of  the  paper  to 
a  certain  tint.  Supposing  the  correct  exposure  of  the  plate  to  be 
3  sees.,  and  it  is  found  that  the  paper  takes  30  sees,  to  darken, 
it  is  obvious  that  dividing  the  actinometer  time  by  10  will  give 
the  correct  exposure,  with  a  certain  stop  and  class  of  picture, 
from  which  the  others  can  be  calculated.  Ordinary  albumenised 
paper,  which  owes  its  darkening  properties  to  chloride  of  silver, 
is  sometimes  used,  and,  although  the  results,  with  certain  modifi- 
cations, are  some  guide,  it  is  obviously  unfair  to  calculate  the 
exposure  of  bromide  of  silver  from  the  action  of  chloride.  The 
term  Photometer  (q.v.)  is  sometimes,  but  erroneously,  applied  to 
such  an  instrument.  Under  the  title  of  Actinograph  Messrs. 
Hurter  and  Driffield  have  devised  a  series  of  slide  rules  based 
on  their  researches  on  the  actinic  value  of  daylight,  which  is 
recommended  for  determining  exposures  in  conjunction  with 
their  system  of  plate  speeds. 

Adapter.  When  using  two  or  more  lenses  of  different  sizes 
it  is  necessary  either  to  have  a  separate  camera  front  for  each 
lens  or  else,  by  the  aid  of  smaller  supplementary  flanges,  to 
screw  the  lens  into  the  largest  flange.  These  supplementary 
flanges  are  called  adapters  ;  the  term  has  also  been  applied  to  a 
supplementary  bellows,  which,  affixed  to  the  back  of  a  small 
camera,  allows  a  larger  plate  to  be  used. 

Aerial  Perspective.  An  artistic  term  used  to  denote  the 
idea  of  distance  in  a  landscape  or  photograph  of  the  same,  which 
depends  upon  the  fact,  that  the  more  remote  the  object  the  less 
forcibly  the  visual  rays  are  perceived  by  the  retina  of  the  human 
eye.  This  feature,  which  lends  so  much  beauty  to  photographs, 
can  only  be  obtained  by  the  use  of  long-focus  lenses,  or  by  the 
use  of  as  large  a  diaphragm  as  possible.  (See  Focus  and 
Diaphragm.) 

Agar-Agar  (Ger.  and  Fr.,  Agar-Agar;  ltal.,  Alga  di  Giava). 

4 


DICTIONARY  OF  PHOTOGRAPHY. 


[Air 


This  is  practically  vegetable  gelatine  obtained  from  species  of 
white  seaweeds  {Fucus  spznosus,  or  Gelidium  come?tm),  common 
on  the  coasts  of  Singapore  and  Straits  Settlements.  It  has  been 
suggested  as  a  substitute  for  gelatine,  but  is  liable  to  give 
emulsions  which  are  full  of  transparent  nodules.  Rebikow 
has  suggested  a  method  of  eliminating  these  nodules,  but  there 
are  no  advantages  which  warrant  its  recommendation  as  a  sub- 
stitute for  gelatine. 

Agate  Burnisher.  A  now  obsolete  device  for  burnishing 
silver  prints.  In  shape  an  agate  burnisher  was  somewhat  similar 
to  a  shorthanded  spade  or  household  meat-chopper. 

Agent.  That  which  has  the  power  of  acting,  or  producing 
effects,  upon  anything  else — e.g.,  light  is  the  agent  which  impresses 
the  image  upon  a  sensitive  plate,  and  the  developer  the  agent 
which  makes  such  image  apparent. 

Air  Bells,  or  Air  Bubbles.  These  annoying  defects  are 
liable  to  make  their  appearances  in  all  sorts  of  out  of  the  way 
places  ;  generally,  too,  where  they  are  not  wanted.  They  may 
occur  in  the  glass  support,  and  if  of  not  large  size,  and  in  the 
face  or  other  prominent  part  of  the  picture,  may  be  ignored  or 
touched  out  on  the  prints.  Air  bubbles  in  the  emulsion  itself 
sometimes  occur,  and  give  rise  to  small  spots  of  bare  glass, 
which  may  be  touched  out  with  a  brush  or  pencil  before  printing 
from  the  negative.  Air  bells  in  the  developer  frequently  adhere 
with  great  tenacity  to  the  gelatine  film,  and  give  rise  to  places  of 
less  density  than  the  surrounding  parts,  or  even  clear  glass.  It 
is  always  advisable  to  pass  the  fingers  over  the  plate  when  first 
covered  with  the  developer,  or  a  flat,  soft  camel's-hair  brush  may 
be  kept  for  this  purpose.  If  a  brush  be  used  care  must  be  taken 
that  it  is  well  washed  after  use  and  does  not  come  into  contact 
with  any  chemical  or  foreign  matter,  which  would  cause  streaks 
on  the  finished  negative. 

Air  Brush.  This  is  an  American  invention,  by  means  of 
which  liquid  colours  can  be  applied  to  enlargements  and  prints 
Air  is  pumped  by  means  of  a  foot-blower  through  a  chamber 
terminating  in  a  fine  orifice,  the  liquid  colour  being  led  to  the 
opening  by  a  movable  needle  or  fine  tube. 

5 


Ala] 


DICTIONARY  OF  PHOTOGRAPHY. 


Alabastrine  Process.  An  old  wet-plate  process  for  im- 
proving the  colour  of  glass  positives.  It  can  be  applied  to 
gelatine  negatives  in  the  following  manner  (absolute  freedom 
from  stains  and  hypo  being  a  sine  qua  non) : — Soak  the  negative 
in  clean  water  till  thoroughly  moist,  and  then  in  following 
solution  :  perchloride  of  mercury,  40  grs.,  dissolved  in  pure 
hydrochloric  acid,  1  drm.  ;  chloride  of  sodium,  20  grs. ;  sulphate 
of  iron,  20  grs. ;  distilled  water,  2  ozs.  Allow  it  to  soak  till 
thoroughly  bleached;  wash,  dry,  and  varnish  with  matt  black 
varnish,  or  back  with  black  velvet. 

Albertype.   See  Collotype. 

Album.  Literally,  anything  white.  Now  used  in  the  sense 
of  a  blank  book,  either  with  openings  for  the  reception  of  photo- 
graphs, or  blank  pages  to  which  they  may  be  affixed. 

Albumen.  An  organic  principle  found  in  both  the  animal 
and  vegetable  kingdoms.  The  purest  form  in  which  it  can  be 
obtained,  and  the  one  in  which  it  is  used  photographically,  is 
the  white  of  egg,  its  chief  use  being  the  preparation  of  albumenised 
paper.  It  may  be  obtained  commercially  in  a  dry  form,  which  is 
the  most  convenient  for  such  purposes  as  the  albumen  substratum 
or  albumen  process. 

Albumenised  Paper.  Paper  coated  with  albumen  and  salt 
This  has  now  become  so  necessary  an  article  that  it  is  prepared 
commercially  so  cheaply  and  in  such  perfection  that  the  ordinary 
amateur  had  much  better  buy  it  already  prepared.  The  following 
short  directions  will  give  some  idea  of  the  method  of  proce- 
dure:— Absolutely  fresh  eggs  must  be  used.  Crack  each  egg 
into  a  separate  cup  or  measure  before  mixing  with  the  bulk,  so 
that  in  case  of  the  yolk  breaking  the  whole  of  the  albumen  may 
not  be  spoilt.  Take  out  the  germ  of  each  egg.  Every  fair-sized 
egg  will  yield  about  7  drms.  of  albumen. 

Albumen      ...       ...  ...       6  ozs.    or  500  c. cm. 

Chloride  of  ammonium  ...  60  grs.     ,,    n  grms. 

Rectified  spirit        ...  ...  96  mins.  „    17  „ 

Distilled  water       ...  ...  14  drms.  „  160  c.cm. 

Dissolve  the  salt  in  the  spirit  and  water,  add  to  the  albumen 
and  beat  with  an  egg-whisk  for  fifteen  minutes  ;  allow  it  to  settle 

6 


DICTIONARY  OF  PHOTOGRAPHY. 


[Alb 


and  filter  it  through  a  tuft  of  cotton-wool,  previously  well  washed 
with  distilled  water.  This  is  sufficient  for  a  quire.  The  paper 
should  be  either  Saxe  or  Rive.  Put  the  albumen  into  a  large 
flat  dish ;  take  the  paper  by  two  opposite  corners,  and  bring 
the  hands  close  together,  so  as  to  make  the  paper  bow  out  in 
the  middle  ;  lay  the  middle  of  the  paper  on  the  surface  of  the 
albumen,  gradually  lowering  the  ends  till  it  rests  on  the  albumen. 
When  the  paper  has  floated  for  a  few  seconds,  bubbles  will 
be  shown  by  the  numerous  puckers ;  lift  the  paper,  and  wet  the 
bubbles  with  a  camel's-hair  brush ;  allow  the  paper  to  float  for 
eighty  seconds — not  longer,  or  the  albumen  will  sink  into  the 
body  of  paper — then  gradually  raise  by  one  corner,  and  suspend 
from  two  corners  to  dry ;  when  thorougly  dry,  roll  between  steel 
rollers,  and  keep  flat.  Double  albumenised  paper  is  made  by 
coagulating  the  first  layer  of  albumen  by  steam,  and  treating  in 
the  same  way  again. 

Albumen  Process.  The  finest,  but  most  difficult,  of  all 
processes  that  are  used  for  lantern-slide  making.  The  plates 
are  slower  even  than  gelatino-chloride  plates,  and  are  therefore 
only  suitable  for  contact  printing  ;  but  the  delicacy  of  results,  the 
fineness  of  the  deposit  and  the  transparency  of  the  shadows 
places  it  facile  princeps.  Glass  plates  are  first  thoroughly  cleaned 
by  brushing  with  nitric  acid  and  water,  rinsed  in  distilled  water, 
and  allowed  to  dry  spontaneously ;  they  are  then  edged  with 
solution  of  indiarubber  (See  Edging),  and  coated  with  an  old 
"  sherry-coloured "  collodion.  As  soon  as  the  film  has  set 
immerse  in  distilled  water  till  all  greasiness  has  disappeared  ;  it 
is  then  ready  for  albumenising.  Take  10  ozs.  of  the  whites  of 
new-laid  eggs,  from  which  the  germs  have  been  removed,  and 
add  gradually,  with  constant  stirring,  I  oz.  of  distilled  water,  to 
which  30  mins.  of  glacial  acetic  acid  have  been  added.  Cover 
with  a  piece  of  muslin,  or  soft  linen,  and  set  aside  for  twenty- 
four  hours  in  a  cool  place.  At  the  expiration  of  this  time  remove 
the  coagulated  scum,  and  filter  the  albumen,  when  it  is  ready  for 
the  iodiser. 

Ammonium  iodide  ...       ...      50  grs.,    or  10  grms. 


„  bromide 
Liquor  ammonia  *88o 
Distilled  water 


5  ,1 
35  mins. 
1  oz. 


1  > 


1  grm. 
6  c.cm. 
85  c.cm. 


7 


Alb] 


DICTIONARY  OF  PHOTOGRAPHY. 


Add  this  to  the  albumen  and  filter.  The  plate  is  coated  with  the 
iodised  albumen  and  drained,  and  a  second  coating  of  albumen 
applied.  The  plate  is  then  allowed  to  dry  spontaneously,  or  by 
a  gentle  heat,  the  latter  being  preferable.  The  plate  is  now  ready 
for  sensitising,  and  as  in  this  condition  it  will  keep  indefinitely  a 
stock  may  be  prepared.  The  plates  are  sensitised  in  a  dipping- 
bath  as  in  wet  collodion,  the  following  being  the  sensitiser  : — 

Nitrate  of  silver    480  grs.,  or    10  grms. 

Distilled  water       ...       ...      10  ozs.  „   100  c.cm. 

Glacial  acetic  acid   ...       ...       1  oz.    ,,     10  c.cm. 

Dissolve  and  add — 

Potassium  iodide    2  grs.  or  0*25  grms. 

Shake  well,  allow  to  stand  for  half  an  hour,  and  filter.  The 
plates  must  be  sensitised  in  yellow  or  orange  light,  and  should 
remain  in  the  bath  for  about  half  a  minute  in  summer  to  one 
minute  in  winter.  After  sensitising,  place  in  a  dish  of  distilled 
water  for  five  minutes,  wash  under  the  tap,  and  dry.  Plates 
thus  prepared  will  keep,  under  proper  conditions,  for  several 
weeks.  The  exposure,  which  should  always  be  to  daylight,  will 
be  about  30  to  40  seconds  under  a  negative  of  average  density. 
The  developer  is  as  follows  : — 

No.  1. 

40  grs.  or  2*5  grms. 
35  mins. ,,  2  c.cm. 
10  ozs.  ,,  300  c.cm. 
12  grs.   ,,   0.6  grms. 

No.  2. 

Silver  nitrate  ...       ...      12  grs.  or  -6  grms. 

Citric  acid    12   ,,        .6  ,, 

Distilled  water       ...       ...       2  ozs.  ,,  56  c.cm. 

For  use  add  two  or  three  drops  of  No.  2  to  No.  1.  Before 
development  give  the  film  an  edging  of  rubber  solution,  and 
place  in  a  dish  of  hot  distilled  water  for  one  or  two  minutes. 
Place  the  developer  in  a  porcelain  dish,  and  heat  gently  by  the 
aid  of  a  spirit  lamp  to  ioo°  F.  ;  place  the  exposed  plate  in  the 

8 


Pyrogallol 
Acetic  acid   . . . 
Distilled  water 
Citric  acid  ... 


DICTIONARY  OF  PHOTOGRAPHY. 


[Alk 


hot  developer,  and  the  image  will  gradually  appear  and  gain 
density,  this  being  accelerated,  if  desired,  by  the  addition  of 
more  No.  2.  The  developer  must  be  maintained  at  the  above 
temperature,  although  errors  in  exposure  may  be  compensated 
for  by  using  a  developer  of  higher  or  lower  temperature.  When 
sufficiently  dense  it  may  be  fixed  in — 

Hyposulphite  of  soda        ...       I  oz.  or  10  grms. 
Water  ...       ...       ...       6  ozs.  ,,  60  c.cm. 

or  a  20-grain  solution  of  cyanide  of  potassium.  These  slides 
may  be  reduced  or  intensified  by  any  of  the  ordinary  methods ; 
though,  for  the  latter  process,  mercuric  chloride,  followed  by 
ammonia,  gives  the  most  satisfactory  tones.  The  image  may  be 
toned  with  the  old  sel  d'or — 

Sat.  sol.  of  hyposulphite  of  soda     2-£  ozs.  or  1200  c.cm. 
Chloride  of  gold     ...       ...  1  gr.     „       1  grm. 


After  washing  and  drying,  the  slides  will  be  ready  for  binding. 

Alcohol  (Ger.,  IVeingeist,  Alkohol ;  Fr.,  Alcool ;  Ital.,  Alcool). 
CH5HO  =  46.  Synonyms:  Rectified  Spirit,  Ethylic  Alcohol, 
Hydrate  of  Ethyl,  Spirits  of  Wine.  It  is  prepared  by  distillation 
from  fermented  saccharine  solutions,  or  any  vinous  fluid.  There 
are  three  strengths  : — 

Absolute  Alcohol.  Contains  but  1  or  2  per  cent,  of  water. 
Specific  gravity,  *8oo. 

Rectified  Spirit.  Contains  16  per  cent,  of  water,  and  is  what 
is  termed  56  degs.  over-proof.    Specific  gravity,  '838. 

Proof  Spirit.  Made  by  diluting  five  parts  of  rectified  spirit 
with  three  of  water. 

Alkali.  This  is  the  antithesis  of  an  acid.  Alkalies  turn 
litmus  paper  blue  which  has  been  reddened  by  an  acid.  They 
precipitate  metals  from  acid  solutions,  as  oxides  or  hydrates. 
Their  chief  characteristic,  however,  is  their  readiness  to  unite 
with  acids  to  form  salts.  The  three  true  alkalies  are  potassium, 
sodium,  and  ammonium. 


Or 


Bichloride  of  platinum 
Water   


1  gr.  or 
1  oz.  „ 


1  grm. 
500  c.cm. 


9 


Alk] 


DICTIONARY  OF  PHOTOGRAPHY. 


Alkaline  Development.   See  Development. 

Alpha  Paper  is  paper  coated  with  a  chlorobromide  emulsion, 
and  was  first  suggested  by  Eder  in  1883.  It  is  intended  for 
development,  and  not  printing  out ;  and  from  the  ease  with  which 
warm  or  cold  tones  can  be  obtained  at  will,  and  from  its  being 
possible  to  obtain  prints  by  its  aid  at  night  which  are  equal  to 
ordinary  printed-out  papers,  has  received  a  good  deal  of  atten- 
tion. Several  formulae  have  been  given  for  this  emulsion-paper. 
Wellington  suggests  the  following  :— 


Solution  A. 


Silver  nitrate... 
Citric  acid  ... 
Distilled  water 


10  parts. 
10  „ 
144  .» 


Solution  B. 


Sodium  chloride 
Potassium  bromide 
Citric  acid 
Gelatine 
Distilled  water 


2  parts. 

4  » 
10  „ 

4  n 

144  r, 


Heat  both  solutions  to  66°  C,  and  add  A  to  B,  shaking 
violently ;  then  add  20  parts  gelatine  previously  swollen  in  water 
and  melted ;  shake  the  whole  well,  and  pour  out  into  a  dish  to 
set ;  allow  it  to  remain  for  twenty-four  hours,  break  it  up,  wash, 
re-melt,  and  coat  the  paper  or  other  support.  One  of  the  ad- 
vantages of  alpha  papers  is  that  it  is  possible  to  obtain  prints  of 
great  beauty,  rivalling  albumen  in  tone,  and  superior  to  them  in 
surface,  without  the  trouble  of  having  to  print  out ;  it  is  a  develop- 
ment printing  process.  A  fault  often  found  with  it,  however,  is 
that  it  is  difficult  to  obtain  a  certain  number  of  prints  from  one 
negative  all  of  one  colour  ;  but  this  is  due  to  faulty  manipulation, 
and  not  to  the  paper.  The  best  method  of  working  it  is  as 
follows  : — Gas  or  some  artificial  light  must  be  used  :  daylight  is 
too  variable.  Assuming  that  we  are  using  a  No.  5  Bray  burner, 
which  is  turned  up  as  full  as  possible  without  flaring.  At  a 
distance  of  9  ins.  from  this  burner  on  the  table,  shelf,  or  wall, 
draw  a  straight  line.  This  is  the  mark  on  which  the  edge  of  the 
printing  frame  should  always  rest.    Having  chosen  your  negative 

10 


DICTIONARY  OF  PHOTOGRAPHY. 


[Alu 


which  we  will  assume  to  be  one  of  the  ordinary  character,  place 
your  paper  in  contact  with  it,  and  set  the  frame  to  the  mark. 
Turn  up  the  gas,  and  give  the  paper  four  different  exposures  of 
90,  100,  no,  and  120  sees.,  covering  part  of  the  frame  up  with 
a  piece  of  black  or  nonactinic  paper  at  each  exposure ;  develop 
the  paper  as  described  below,  and  you  will  at  once  have  a  guide 
to  the  correct  exposure  for  any  particular  colour  for  that  par- 
ticular negative.  It  must  be  remembered  that  alpha  prints  can 
be  toned ;  but  for  a  photographic  purple  the  developed  print 
should  be  a  pinkish  violet  after  development,  and  this  is  the 
best  colour  to  aim  at  for  all  other  tones.  Having  found  the 
correct  exposure  for  the  particular  negative,  expose  as  many 
pieces  of  paper  as  prints  are  required,  taking  care  to  give  exactly 
the  same  exposure  from  a  metronome  or  watch,  and  then  pro- 
ceed to  develop  them.  Either  ferrous  oxalate,  hydroquinone, 
eikonogen,  or  glycin  can  be  used,  but  for  warm  tones  hydro- 
quinone is  preferable ;  and  the  formulae  for  these  developers 
suggested  for  bromide  paper  may  be  used  if  dilated  with  two  or 
three  parts  of  water  and  some  bromide  of  potassium  added. 
The  final  tone  depends  to  a  great  extent  on  to  the  exposure, 
long  exposures  tending  to  give  warmer  tones.  If  the  iron 
developer  is  used  the  prints  must  be  placed  in  an  alum  and 
citric  acid  clearing-bath  for  two  minutes,  well  washed,  and  then 
fixed.  Alpha  prints  may  be  toned  in  a  combined  bath,  when  of 
course  fixing  need  not  be  done,  or  preferably  in  the  following  : — 

Chloride  of  gold      ...       ...       ...       ...       1  gr. 

Calcium  choride  (crystal)   10  ,, 

Water    10  ozs. 

Place  the  prints  in  this  after  well  washing  out  the  fixing  solution, 
and  tone  till  the  desired  colour  is  reached.  The  prints  only  want 
well  washing  and  drying  to  be  ready  for  mounting.  Alpha  prints 
can  be  rolled  and  burnished,  provided  too  great  a  heat  be  not 
used.  Over-exposure  gives  flat  prints  without  any  depth  in  the 
shadows  and  without  pure  whites,  whilst  under-exposure  gives 
harsh  prints  with  greenish  tones. 

Alum.  Under  this  name  a  series  of  important  double  salts 
are  classed.  These  salts  are  characterised  as  being  double 
sulphates  of  monatomic  and  triatomic  metals  crystallising  in 

1 1 


Alu]  DICTIONARY  OF  PHOTOGRAPHY. 

cubes  or  octahedra,  and  containing  24  molecules  of  water  of 
crystallisation,  and  have  therefore  the  common  formula  ofM2'S04, 
M2"'3S04,  24H2O.  The  principal  alums  are  ammonia  alum, 
chrome  alum,  and  potash  alum. 

Ammonia  Alum  (Ger.,  Ammoniakalaun ;  Fr.,  Alun  Ammoni- 
acal;  Ital.,  Allume  di  Ammoniacd).  (NH4)2S04A123S0424H20 
=  560.  This  is  manufactured  in  a  similar  manner  to  potash 
alum,  with  the  exception  that  ammonium  sulphate  is  utilised 
instead  of  potassium  chloride.  Solubility :  1  in  7  of  cold  water, 
I  in  o*2  of  boiling  water,  1  in  2  of  alcohol. 

Chrome  Alum  (Ger.,  Chromalaun;  Fr.  Alun  de  Chrome ;  Ital., 
Allume  di  Cromo) .  K2S04Cr  3S0424H20  =  951.  A  deep  purple 
crystalline  salt,  soluble  1  part  in  10  of  cold  water,  insoluble  in 
alcohol.  Its  solution  is  purple  by  reflected,  and  reddish  by 
transmitted,  light.  It  is  used  for  clearing  negatives,  etc.  It  is 
also  used  in  the  preparation  of  emulsions  for  dry  plates  to  prevent 
frilling. 

Potash  Alum  (Ger.,  Alaun ;  Fr.,  Alun;  Ital.,  Allume  comtme), 
K2S04A123S04,  24^0  =  948.  Is  found  native  in  some  places, 
but  is  usually  made  from  aluminous  clay.  It  is  used  for  render- 
ing the  films  of  gelatine  less  liable  to  mechanical  injury,  by 
hardening  them,  and  also  clears  them  from  stains  (see  Clearing 
Bath).  It  has  also  been  recommended  as  a  Hypo-eliminator 
(q.v.),  but  its  action  and  benefit  is  doubtful.  Solubility :  9-5  in 
100  of  cold  water,  10  in  8  of  boiling  water  ;  insoluble  in  alcohol 
and  ether. 

Aluminium  (Ger.  and  Fr.,  Aluminium;  Ital.  Alluminio). 
Al  =  27.  A  silvery  white  metal,  obtained  principally  from  the 
chloride.  It  has  been  used  to  replace  brass  for  lens  mounts,  and 
camera  fittings  on  account  of  its  lightness,  its  weight,  bulk  for  bulk, 
being  less  than  half  that  of  brass.  It  has  also  been  used  as  a 
substitute  for  magnesium,  for  flash  light,  and  has  been  suggested 
by  Lainer  as  a  means  of  precipitating  silver  from  residues. 

Aluminium  Chloride  (Ger.,  Aluminiumchlorid ;  Fr.,  Chlorure 
d'aluminium  ;  Ital.,  Clorure  di  alumin).  A12C16  is  formed  by 
heating  alumina  and  charcoal  and  passing  over  it  a  stream  of 
chlorine  gas.  It  occurs  in  white  tabular  crystals  which  are 
hygroscopic.  It  is  soluble  in  water,  alcohol,  and  ether.  It  has 
been  suggested  as  a  toning  agent  for  gelatino-chloride  prints. 

12 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ami 


Aluminium  Sulphate  (Ger.,  Alumininmsulfat y  Fr.,  Sulfate 
d  'aluminium ;  Ital.,  Solfato  di  alumin).  A123(S04),  i8H26  is 
formed  by  dissolving  aluminium  hydroxide  Al2(OH)6  in  sulphuric 
acid.  It  has  been  suggested  as  a  substitute  for  the  ordinary  and 
chrome  alums,  for  hardening  gelatino-chloride  prints,  and  in 
emulsion  making. 

Aluminium  Sulphocyanide  (Ger.,  Aluminium  sulphocyanid 
Rhodanaluminium ;  Fr.,  Sulfocyanure  d 'aluminium;  Ital.,  Sol- 
focianuro  d'aluminio).  Can  be  formed  by  double  decomposition 
of  barium  sulphocyanide  with  aluminium  sulphate.  It  is  volatile, 
decomposing  below  21 2°  F.,  and  forms  a  dark  violet  red  crystalline 
compound ;  but  is  very  difficult  to  obtain  in  a  crystalline  form  as 
it  is  very  deliquescent. 

Amber  (Ger.,  Grauer  Amber,  Bernstein;  Fr.,  Ambre ;  Ital., 
Ambra).  A  fossil  resin  from  an  extinct  species  of  pine.  It  is 
used  for  preparing  a  Varnish  {g.V.). 

Ambrotype.    An  American  synonym  for  Ferrotype  (q.v.). 

Amidol  (Ger.,  Fr.,  Ital.,  Amidol).  CGH3OH(NH,):,  =  124. 
Synonym :  Diamidophenol.  The  peculiar  characteristic  of  this 
substance  is  that  it  will  develop  without  the  addition  of  alkali. 
It  is  a  white  crystalline  powder  readily  soluble  in  water.  The 
aqueous  solution  does  not  keep  well,  not  even  with  sulphite,  but 
soon  loses  its  developing  power ;  it  is  preferable  therefore  to 
keep  it  dry  and  dissolve  as  required.  It  is  advisable  to  keep  a 
stock  solution  of 

Sodium  sulphite    5  ozs.  or  250  grins. 

Distilled  water    ...    20        ,,  1000 

For  ordinary  negative  work  take 

Amidol  dry   i\  grs.  or  -5  grms. 

Sol.  sod.  sulphite    \  oz.      5  cc. 

Sol.  bromide  of  potash  10%         ...  10  drops  -5  „ 

Distilled  water    1  oz.    100  ,, 

To  accelerate  the  development  the  strong  solution  of  sodium 
sulphite  may  be  added  by  degrees.  Another  form  of  developer 
has  been  proposed  which,  however,  one  can  only  assume  to  be 

l3 


Ami]  DICTIONARY  OF  PHOTOGRAPHY. 

based  on  the  desire  of  being  the  author  of  a  new  formula,  which 
in  our  hands  possesses  no  advantages.    It  is  the  following  : — 

Solution  A. 

Water    20  ozs.  or  100  c.cm. 

Potassium  metabisulphite  ...       2    ,,         10  grms. 
Amidol    1    ,,    ,,     5  „ 

This  solution  will  keep  for  a  very  long  time  if  well  corked. 

Solution  B. 

Water    20  ozs.  or  100  c.cm. 

Soda  crystals    2    ,,    „    10  grms. 

Solution  C. 

Water       .  ...       ...       ...     20  ozs.  or  100  c.cm. 

Sodium  sulphite,  cryst.,  pure       4    ,,  10  grms. 

Results  similar  to  pyro  may  be  obtained  with 

Solution  A  ...       ...       ...       ...       ...      10  parts. 

B    ...         6—10  „ 

Water    70  ,, 

Bromide  (1  :  10)     ...       ...       ...       ...       3  „ 

But  this  formula  may,  be  considerably  modified,  according  to 
requirements;  it  is  not,  however,  advisable  to  increase  the  quantity 
of  alkali,  for  fear  of  inducing  fog.  For  over-exposed  plates,  add 
the  solution  B  in  the  above  formula  little  by  little,  until  the 
desired  effect  is  obtained,  never  exceeding  the  amount  above 
prescribed.  Images  of  a  softer  character  are  obtained  as 
follows : 

Solution  A   10  parts. 

B   20—40  „ 

Water    70  „ 

Bromide  (1  :  10)   \ — J  „ 

Solution  D. 

Water         ...       ...       ...  ...       ...     20  ozs. 

Sodium  sulphite,  pure  cryst.  ...       ...       £  oz. 

Amidol  ...  2  ozs. 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ami 


This  solution  keeps  colourless  for  a  long  time  in  full  and  air- 
tight vessels.  When  opened  it  goes  from  yellow  to  red,  which, 
however,  does  not  affect  the  developing  power,  or  coloration  of 
plates. 

For  use  take — 

Solution  D   5  parts. 

Water    50—70 

Solution  C   20 — 30  ,, 

Bromide  (1  :  10)    ll  ,, 

This  formula  also  has  the  advantage,  by  gradually  adding 
solution  C,  of  controlling  development  up  to  the  point  desired, 
which  is  specially  important  for  over-exposed  plates.  As  the 
image  loses  on  fixing,  it  is  recommended  to  develop  more 
strongly. 

For  Bromide  Paper.  Both  for  prints  and  enlargements  either 
of  the  above  formulae  may  be  used,  and  the  freedom  from  stains 
will  prove  of  great  advantage.  With  diluted  solutions  clear  grey 
tones  are  obtained. 

For  Chloride  Plates  and  Lantern  Slides.  Transparencies  of 
the  blackest  tones  are  developed  with  : — 

Water    20  ozs. 

Sodium  sulphite,  cryst.,  pure       ...       ...       1  oz. 

Amidol    4°  grs. 

Warmer  tones  are  obtained  through  longer  exposure  and  the 
liberal  addition  of  bromide,  even  up  to  one  ounce  in  the  four- 
ounce  developer.  Practically  the  ordinary  methods  of  develop- 
ment may  be  followed  with  amidol — namely,  for  over-exposure, 
dilution  of  the  developer  with  water,  increase  of  bromide,  or 
decrease  of  the  accelerator ;  for  under-exposure  the  contrary 
directions  of  course  hold  good.  Amidol  is  likely  to  prove  of 
great  value  especially  in  instantaneous  work  :  it  gives  fine  steely 
blue  or  grey-black  images,  and  there  is  no  tendency  to  stain.  The 
author  has  found  that  for  subjects  with  great  contrasts,  under- 
exposed plates,  and  portraiture,  this  developer  will  place  a  great 
power  in  the  hands  of  the  intelligent  worker,  because  the  images 

*5 


Amm]  DICTIONARY  OF  PHOTOGRAPHY. 


given  are  soft  and  harmonious,  and  one  is  thus  enabled  to 
intensify,  to  gain  the  requisite  density,  without  getting 
harshness. 

Ammonia  (Ger.,  Wasseriges  Ammonia,  Salimakgeist ;  Fr., 
Ammoniaque ;  Ital.,  Ammoniacd).  NH3=i7.  Is  an  extremely 
volatile,  pungent  gas,  but  is  only  known  to  photographers  as  a 
solution  in  water,  termed  liquor  ammoniae  fortissimus.  Specific 
gravity,  *88o,  containing  about  35  per  cent,  of  NH3.  It  should 
be  kept  in  stoppered  bottles,  as  the  gas  is  freely  evolved  at 
ordinary  temperatures,  carbonic  acid  being  absorbed  from 
the  air,  forming  carbonate  of  ammonia.  It  is  used  in  alkaline 
development  as  an  accelerator  for  pyrogallol.  The  fumes  are 
extremely  suffocating,  causing  sudden  contraction  of  the  glottis 
and  consequent  death.  Its  use  in  ill-ventilated  dark-rooms  is 
said  to  cause  permanent  irritation  of  the  mucous  membranes  of 
the  throat,  nose,  and  eyes.  There  is  a  weaker  strength,  known 
as  liquor  ammoniae  (specific  gravity,  '936),  only  one-third  the 
strength  of  the  liq.  ammon.  fort. 

Ammonium  Bichromate  (Ger.,  Dichromsdures  Ammoniak; 
Fr.,  Bichromate  d'ammoniaque  ;  Ital.,  Bicromato  d' ammoniacd). 
(NH4)2Cr207=253.  Made  by  neutralising  chromic  acid  with 
ammonia.  It  is  used  occasionally  instead  of  the  potash  salt  in 
photo-mechanical  printing, 

Ammonium  Bromide  (Ger.,  Bromammonium ;  Fr.,  Bromure 
d' ammonium;  Ital.,  Bromuro d'ammonio).  NH  4Br  =  98.  Made 
by  neutralising  hydrobromic  acid  with  ammonia,  or  by  double 
decomposition  from  bromide  of  calcium.  Its  chief  use  is  as  a 
Restrainer  (q.v.),  but  it  is  sometimes  used  in  the  preparation  of 
gelatino-bromide  emulsion.  Solubility  :  1  in  i£  of  cold  water,  1 
in  13  of  alcohol. 

Ammonium  Carbonate  (Ger.,  Ammoniumcarbonat,  or, 
Kohlensaures  ammoniak ;  Fr.,  Carbonate  d 'ammoniaque ;  Ital., 
Carbonato d ammoniacd).  2(NH4HC03)NH4C02NH.j=  342.  Made 
by  sublimation  from  chalk  and  sal-ammoniac.  It  is  used 
occasionally  for  development,  but  is  not  so  suitable  as  liquor 
ammoniae.    Solubility :  1  in  4  of  cold  water,  sparingly  in  alcohol. 

16 


DICTIONARY  OF   PHOTOGRAPHY.  [Anim 


Ammonium  Chloride  (Ger.,  Chlorammonium,  Salmiak; 
Ft.,  Chlorure  d'ammoniwn ;  ItaL,  Cloridrato  d'ammoniaca). 
NH4C1  =  53*5.  Synonym  :  Muriate  of  Ammonia,  Hydrochlorate 
of  Ammonia,  Sal-ammoniac.  Is  prepared  by  neutralising 
ammoniacal  gas  liquor  with  hydrochloric  acid  and  subsequent 
purification.  It  is  principally  used  for  salting  albumenised  paper, 
and  for  preparing  chloride  emulsion.  Solubility  :  1  in  3  of  cold 
water,  1  in  55  of  alcohol. 

Ammonium  Citrate  (Ger.,  A?nmo?iiumcit?'at ;  Fr.,  Citrate 
d,a?n?noniaque ;  ItaL,  Citrato  d,a?7imoniaca).  (NH4)3C6H-07 
=  124.  This  is  usually  met  with  in  the  form  of  solution,  the  salt 
itself  being  so  deliquescent,  that  it  is  an  extremely  difficult 
matter  to  keep  it.  It  may  be  conveniently  prepared  by  exactly 
neutralising  citric  acid  with  solution  of  ammonia  or  carbonate  of 
ammonia,  the  following  being  the  method  adopted  by  the 
British  Pharmacopoeia. 

Citric  Acid   ...      12  parts. 

Strong  solution  of  ammonia         ...       ...      11  „ 

Neutralise  the  acid  with  the  ammonia,  and  add  sufficient  dis- 
tilled water  to  make  24  parts.  This  can  be  preserved  as  a  stock 
solution  for  use  in  alkaline  development  (see  Development). 
It  has  been  employed  in  the  preparation  of  gelatino-chloride 
emulsions,  but  its  principal  use  is  as  a  restrainer  in  development 
of  chloride  emulsions. 

Ammonium  Iodide  (Ger.,  Jodammonium ;  Fr.,  Iodnre 
d'ammonintn  ;  lta\.,  foduro  d' ammonia).  NH4I  =  145.  Made 
by  neutralising  hydriodic  acid  with  ammonia.  It  is  much  used 
for  making  Iodised  Collodion  (q.v.).  Solubility  :  4  in  3  of  water, 
1  in  4  of  alcohol,  I  in  20  of  ether,  and  1  in  20  of  alcohol  and 
ether. 

Ammonium  Oxalate  (Ger.,  Ammoniuthoxalat;  Fr.,  Oxalate 
d'ammo?thi?Ji,  or,  Oxalate  neutre ;  Ital.,  Ossalato  di  ammoniacd). 
(NH4).,C204  =  124.  Made  by  neutralising  oxalic  acid  with 
ammonia.  It  has  been  recommended  lately  for  preparing  the 
paper  for  platinotype  printing.  Solubility:  1  in  3  of  water; 
insoluble  in  alcohol. 

17  c 


Amm]  DICTIONARY  OF  PHOTOGRAPHY. 

Ammonium  Sulphide  (Ger.,  Ammoniumsuljid,  or,  Schwef el- 
ammonium ;  Fr.,  Sulf hydrate  d  'ammoniaque ;  Ital.,  Solfidrato 
d' ammoniacd).  (NHJ2S  =  68.  Synonym:  Sulphuret  of  ammonia. 
Prepared  by  passing  sulphuretted  hydrogen  through  ammonia 
solution  until  the  gas  ceases  to  be  absorbed  and  the  adding  an 
equal  volume  of  ammonia  to  that  originally  used.  It  is  used  in 
Intensification  (q.v.)  to  blacken  the  white  image  obtained  by 
bleaching  the  negative  with  mercuric  chloride.  A  caution  is 
necessary  as  to  the  use  and  storage  of  this  in  any  room  where 
sensitive  surfaces  of  any  kind  are  kept,  as  liable  to  blacken  the 
same  without  exposure  to  light. 

Ammonium  Sulphocyanate  (Ger.,  Rhodanammonium ;  Fr., 
Sulfocyanure  d' ammonium;  Ital.,  Rodanuro,  or,  Solfocianuro 
d'ammonio).  NH4CnS  =  76.  A  compound  of  sulphocyanic  acid 
and  ammonia.  Also  prepared  commercially  by  boiling  powdered 
sulphur  with  ammonium  cyanide  which  is  obtained  as  a  refuse 
from  coal  tar.  It  is  used  for  toning  gelatino-chloride  printing- 
out  papers.  It  has  also  been  recommended  as  a  fixing  agent 
instead  of  hypo,  but  from  its  comparatively  high  price,  without 
any  increased  advantages,  it  is  hardly  likely  to  come  into  general 
use.    It  is  a  very  deliquescent  salt,  soluble  also  in  alcohol. 

Amphitype.  A  curious  process  which  was  discovered  by 
Sir  John  Herschel,  who  thus  describes  his  method  of  pro- 
cedure : — 

"Paper  proper  for  producing  an  amphitype  picture  may  be 
prepared  either  with  the  ferro-tartrate  or  the  ferro-citrate  of  the 
protoxide  or  the  peroxide  of  mercury,  or  of  the  protoxide  of  lead, 
by  using  creams  of  these  salts,  or  by  successive  application  of 
the  nitrates  of  the  respective  oxides,  singly  or  in  mixture,  to  the 
paper,  alternating  with  solutions  of  the  ammonio-tartrate  or 
ammonio-citrate  of  iron;  the  latter  solution  being  last  applied, 
and  in  more  or  less  excess.  Paper  so  prepared  and  dried  takes 
a  negative  picture  in  time  varying  from  half-an-hour  to  five  or 
six  hours,  according  to  the  intensity  of  the  light ;  and  the  im- 
pression produced  varies  in  apparent  force,  from  a  faint  and 
hardly  perceptible  picture  to  one  of  the  highest  conceivable 
fulness  and  richness  both  of  tint  and  detail,  the  colour  in  this 
case  being  a  superb  velvety  brown.  This  extreme  richness  of 
effect  is  not  produced  except  lead  be  present,  either  in  the 

18 


DICTIONARY  OF  PHOTOGRAPHY. 


[Amy 


ingredients  used  or  in  the  paper  itself.  It  is  not,  as  I  originally 
supposed,  due  to  the  presence  of  free  tartaric  acid.  The  pictures 
in  this  state  are  not  permanent.  They  fade  in  the  dark,  though 
with  very  different  degrees  of  rapidity,  some  (especially  if  free 
tartaric  or  citric  acid  be  present)  in  a  few  days ;  while  others 
remain  for  weeks  unimpaired,  and  require  whole  years  for  their 
total  obliteration.  But  though  entirely  faded  out  in  appearance, 
the  picture  is  only  rendered  dormant,  and  may  be  restored, 
changing  its  character  from  negative  to  positive,  and  its  colour 
from  brown  to  black  (in  the  shadow),  by  the  following  process : — 
A  bath  being  prepared  by  pouring  a  small  quantity  of  solution  of 
pernitrate  of  mercury  into  a  large  quantity  of  water,  and  letting 
the  subnitrated  precipitate  subside,  the  picture  must  be  immersed 
in  it  (carefully  and  repeatedly  clearing  off  the  air-bubbles),  and 
allowed  to  remain  till  the  picture  (if  anywhere  visible)  is  entirely 
destroyed,  or,  if  faded,  till  it  is  judged  sufficient  from  previous 
experience  ;  a  term  which  is  often  marked  by  the  appearance  of  a 
feeble  positive  picture  of  a  bright  yellow  hue  on  the  pale  yellow 
ground  of  the  paper.  A  long  time  (several  weeks)  is  often 
required  for  this,  but  heat  accelerates  the  action,  and  it  is  often 
complete  in  a  few  hours.  In  this  state  the  picture  is  to  be  very 
thoroughly  rinsed  and  soaked  in  pure  warm  water,  and  then 
dried.  It  is  then  to  be  well  ironed  with  a  smooth  iron,  heated 
so  as  barely  not  to  injure  the  paper,  placing  it,  for  better  security 
against  scorching,  between  smooth  clean  papers.  If,  then,  the 
process  has  been  successful,  a  perfectly  black  positive  picture 
is  at  once  developed.  At  first  it  most  commonly  happens  that 
the  whole  picture  is  sooty  or  dingy  to  such  a  degree  that  it  is 
condemned  as  spoiled,  but  on  keeping  it  between  the  leaves  of 
a  book,  especially  in  a  moist  atmosphere,  by  extremely  slow 
degrees  this  dinginess  disappears ;  and  the  picture  disengages 
itself  with  continually  increasing  sharpness  and  clearness,  and 
acquires  the  exact  effect  of  copperplate  engraving  on  a  paper 
more  or  less  tinted  with  pale  yellow." 

Amy!  Acetate  (Ger.,  Amylacctat;  Fr.,  Acetate  d  amyle  ; 
Ital.,  Acetato  d'amilc).  C5HnC3H302=  130.  Synonym:  Essence 
of  Jargonelle  pears.  Prepared  by  distilling  1  part  of  sulphuric 
acid,  1  part  of  amylic  alcohol,  and  2  parts  acetate  of  potash.  The 
distillate  is  purified  by  washing  with  water,  dried  with  calcium 

19 


Amy] 


DICTIONARY  OF  PHOTOGRAPHY. 


chloride,  and  then  redistilled  from  a  mixture  of  massicot  (oxide 
of  lead),  which  absorbs  any  free  acetic  acid.  It  is  a  colourless 
liquid  with,  at  first,  a  fruity  smell,  but  which  soon  becomes  in- 
tensely nauseous,  and  gives  rise  to  vertigo  and  headache.  It  is 
insoluble  in  water,  but  soluble  in  all  proportions  in  alcohol  and 
ether.  It  boils  at  1370  F.,  and  burns  with,  brilliant  flame,  which 
is,  however,  richer  in  the  more  refrangible  rays  than  the  violet. 
It  is  used  in  the  amyl  acetate  lamp  {q.v.). 

Amyl-Acetate  Lamp.  This  instrument  was  devised  in 
1884  by  Hefner-Altenek,  and  was  adopted  by  the  International 
Congress  of  Photography  in  Paris  in  1889  as  a  convenient 
standard  light  for  photographic  purposes.  Amyl  acetate  is  burnt 
in  it  with  a  cotton  wick,  the  internal  diameter  of  the  wick  tube 
should  be  5  mm.,  and  the  height  of  the  flame  25  mm.  1  cm. 
from  the  axis  of  the  flame  is  placed  a  thin  metal  chimney,  in 
which  is  a  small  aperture  4  mm.  broad  and  30  mm.  long,  and 
this  can  be  shifted  up  and  down  so  as  to  bring  it  opposite  the 
brightest  part  of  the  flame.  The  amyl  acetate  should  have  a 
constant  boiling  point  of  1380  C,  and  be  free  from  acetic  acid  and 
water.  The  spectral  composition  of  the  flame  is  similar  to  that 
of  a  candle,  and  compared  to  the  English  standard  candle,  setting 
the  amyl-acetate  lamp  as  =1,  the  candle  =  1-140.  All  metallic 
parts  of  the  lamp  should  be  made  of  fine  silver,  as  the  fluid  so 
corrodes  brass  and  other  metals  as  to  render  them  useless. 

Angle,  Mid.  This  is  a  term  applied  to  a  certain  class  of  lens 
which  has  a  focal  length  intermediate  between  the  ordinary  rapid 
rectilinear  and  the  so-called  wide-angle. 

Angle  of  View,  or  Width  of  Angle.  It  is  sometimes 
essential  to  know  the  angle  inclosed  by  a  lens,  and  for  this 
purpose  it  is  only  necessary  to  divide  the  diameter  of  its  field  by 
the  focus,  when  reference  to  the  following  tables  will  at  once  give 
the  result.  A  good  deal  of  discussion  has  arisen  as  to  the  meaning 
of  the  term,  "  angle  of  view,"  but  notwithstanding  what  has  been 
said  to  the  contrary,  the  simplest  way  out  of  the  difficulty  is  to 
limit  the  term  to  the  definition  given  above,  and  to  explain  the 
angle  included  by  the  lens  on  a  given-sized  plate  as  the  picture 
angle.  If  this  is  adhered  to  we  avoid  several  difficulties.  Mr. 
W.  Rice  suggests  the  following  simple  formula  : — 

20 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ang 


Let 


P  =  length  of  plate. 
F  =  focus  of  lens. 


Then 


Angle 


63  P 


Or,  exp  .ssed  in  words : — Multiply  the  base  line  of  plate  by  63 
and  di  ide  the  product  by  the  length  of  focus,  added  to  \  of  the 
diagonal  of  the  plate. 

Example: — What  is  the  angle  given  by  a  10-in.  lens  on  a 
12-in.  plate  ? 


This  formula  will  only  apply  when  the  angles  included  are  less 
than  900.  When  the  angle  is  greater  than  900  the  following 
should  be  used  : — 


Or,  expressed  in  words  : — Subtract  from  180  the  quotient  obtained 
by  dividing  126  times  the  focus  of  the  lens  by  \  the  base  line  of 
the  plate,  added  to  twice  the  focus  divided  by  5. 

Example : — What  is  the  angle  included  by  a  4-in.  lens  on  a 
12-in.  plate? 


126  x    4   =  504. 
12  -~-  2  =  6. 
(4  x  2)  -f-    5    =  |. 
6  +     f        7  ■ 
5°4  -r  1%  =  61. 

180  —  61    =  1  i9°approximateangle  included.* 


One  of  the  most  usual  methods  is  by  means  of  the  following 
plan.    Draw  a  straight  line  a  b  equal  in  length  to  the  longer  base 


12  x  63 
10  +  V 
756  -f  I2| 


=  756. 
=  I2f 

=    6i°  practically. 


Angle  =  1800  — 


126  F 
P  2F 
2+  5 


For  Steinheil's  tables  of  angles  see  Appendix. 
21 


Ang"]  DICTIONARY  OF  PHOTOGRAPHY. 

of i the  plate  used,  bisect  this  accurately  at  c,  from  c  draw  a  per- 

D 


Fig.  2. 

A  d  b,  which  may  be  measured  by  laying  a  protractor  on  it  and 
reading  off  the  degrees  included.    For  those  who  may  not  have 


22 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ang 


a  protractor  handy,  the  diagram,  fig.  2,  is  given,  which  may  be 
copied  on  a  lantern  plate,  and  the  developed,  fixed,  and  varnished 
negative  used  as  a  protractor. 

Angle,  Wide.  Applied  to  certain  forms  of  lenses  which 
embrace  a  larger  amount  of  view  than  the  usual  run  of  lenses. 
Wide-angle  lenses  exaggerate  perspective  most  painfully,  in 
increasing  the  apparent  size  of  near  objects  entirely  out  of  all 
proportion  with  those  more  distant.  As  the  angle  of  view  of 
the  human  eye  does  not  exceed  about  50°  no  lens  for 
general  work  should  be  employed  which  would  include  a  greater 


angle  than  500.  Practically  a  lens  includes  a  wide  angle, 
or  a  large  amount  of  subject,  only  when  its  focus  is  short  as 
compared  to  the  plate  with  which  it  is  used.  The  diagram 
(fig.  3)  may  make  this  clear.  Let  us  assume  that  l  is  the  optical 
centre  of  a  lens,  which  will  cover  a  half-plate,  cc'.  The  same 
lens  will  also  cover  a  quarter-plate,  dd'  ;  it  will  also  cover  a 
whole  plate,  bb' ;  and  a  10  by  8  ;  and  a  12  by  10.  Therefore 
with  the  quarter-plate  it  would  be  a  narrow  angle  or  long 
focus,  with  the  half-plate  an  ordinary  angle,  on  a  whole-plate 
a  mid-angle,  on  a  10  by  8  a  wide-angle,  on  a  12  by  10  a  wider 
angle. 


J3' 


A 


Fig-  3- 


Ang]  DICTIONARY  OF  PHOTOGRAPHY. 

Aliglol.  Under  this  name  was  introduced  an  English  manu- 
factured Eikonogen  (g.v.'). 

Angular  Aperture  is  the  relation  borne  by  the  working 
diameter  of  a  lens  to  its  focal  length.  The  wider  the  angular 
aperture  the  less  the  depth  of  focus  and  covering  power  of  the 
lens.    This  is  well  seen  in  a  portrait  lens. 

Aniline  (Ger.,  Anilin;  Fr.,  Aniline;  Ital.,  Anilina).  C6H5NH 
=  93.  Synonym  :  Phenylamine,  Amidobenzine.  It  is  prepared 
commercially  by  the  reduction  of  nitrobenzine  by  heat,  steam, 
iron  filings,  and  hydrochloric  acid.  Solubility :  3  in  100  of  cold 
water ;  very  soluble  in  alcohol,  ether,  and  benzine.  It  is  used  in 
the  aniline  process  (g.v.),  and  also  as  a  base  from  which 
numerous  colouring  matters  used  in  orthochromatic  photography 
are  derived. 

Aniline  Process.  In  1865  Willis  patented  this  process  which 
consists  of  impregnating  paper  with  ammonium  bichromate  and 
phosphoric  acid,  drying,  and  then  exposing  under  a  negative  to 
the  action  of  light,  and  subjecting  it  to  the  fumes  of  aniline,  by 
which  means  aniline  colours  were  formed.  Reynolds,  Dawson, 
Wild,  and  others,  experimented  with  this  process  which  has 
found  but  little  use  in  practice.  H.  W.  Vogel  suggests  the 
following  method  of  procedure  : — 

Sensitising  Solution. 

Potassium  bichromate    1  parts. 

Phosphoric  acid,  Sp.  Gr.  1*124    ...       ...  10  „ 

Water         ...       ...       ...       ...       ...  10  „ 

Good  paper,  such  as  Rives  or  Saxe,  is  allowed  to  float  on  this 
for  one  minute,  and  then  quickly  dried.  It  is  then  exposed 
under  negative  or  line  drawing,  and  developed  by  placing  in  the 
bottom  of  a  box,  to  the  lid  of  which  is  affixed  a  sheet  of  blotting 
paper  impregnated  with  commercial  aniline  1  part,  benzine  16 
parts.  The  image  appears  fairly  quickly  (in  a  few  minutes),  and 
of  a  greenish-blue  black,  which  turns  to  blue  when  the  prints 
are  soaked  in  water.  If  the  fuming  is  carried  on  for  some  time 
the  tones  become  blacker.  With  over-exposure  the  ground 
becomes  tinged,  and  this  may  be  removed  by  alternately  bathing 
in  dilute  sulphuric  acid  i-ioo,  or  in  hydrochloric  acid  5*100,  and 

24 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ape 


washing  and  then  bathing  in  dilute  ammonia.  Philippe  suggested, 
in  1884,  floating  gelatinised  paper  on  10  per  cent,  solution  of 
bichromate  of  potash  and  ammonia.  After  exposure  the  print  is 
laid  in  1  per  cent,  solution  of  potassium  cyanide  till  the  whites 
are  clear,  then  rinsed  and  developed  in 

Anilin    ...       ...       ...      10  parts. 

Oxalic  acid  ...       ...       ...       ...       ...      10  ,, 

Water         ...    ...       ...  100 

In  1866  Endemann  suggested  the  use  of  vanadic  acid.  Well- 
sized  paper  is  sensitised  with 

Salt   480  grains,  or     5  grms. 

Potassium  bichromate       ...  480  5  ,, 

Sodium  vanadiate   320    ,,  3-3 

Water         ...    20  ozs.      „  100  c.cm. 

When  dissolved  add  the  following  mixture  after  it  has  become 
cold — 

Sulphuric  acid         ...       ...       2  ozs.  or  10  c.cm. 

Water    10  „     „  50  „ 

When  the  paper  is  dried  it  is  exposed  under  a  negative  or 
drawing  for  about  7  minutes,  and  then  exposed  to  the  vapour 
from  a  heated  mixture  of  1  part  of  aniline  and  50  parts  of  water. 
The  image  then  appears  brown,  and  the  print  is  left  in  a  room 
full  of  steam  for  two  hours,  or  till  the  image  turns  black,  and 
finally  washed  in  1  :  6  ammonia  water. 

Allthotype.  A  process  yielding  exceedingly  fugitive  prints, 
depending  for  its  principle  upon  the  bleaching  action  of  light 
upon  chlorophyll  and  other  vegetable  juices,  when  the  same  are 
spread  upon  paper  and  exposed  under  a  negative. 

Antiplanat.  A  term  applied  to  a  particular  type  of  lens 
constructed  by  Steinheil. 

Aperture  of  a  Lens,  Working.  By  this  term  is  meant  such 
part  of  the  surface  of  the  lens  which  is  actually  utilised  in 
impressing  the  image  of  the  plate.  Many  amateurs  suppose 
that  the  working  aperture  of  the  lens  is  the  diameter  of  the 

25 


Apl] 


DICTIONARY  OF  PHOTOGRAPHY. 


diaphragm,  others  that  the  whole  surface  of  the  lens  is  always 
utilised ;  but  this  is  not  so.  The  following  method  will  prove 
the  working  aperture  of  any  doublet  lens,  which  varies  with 
each  separate  diaphragm: — Rack  the  camera  out  to  the  true 
equivalent  focus  of  the  lens ;  replace  the  focussing  screen  by  a 
sheet  of  cardboard,  in  the  exact  centre  of  which  is  a  minute  hole 
(a  pinhole  will  do) ;  behind  this,  exactly  level,  place  a  strong 
light,  such  as  a  paraffin  lamp,  and  it  will  be  found  on  looking  at 
the  lens  that  when  a  diaphragm  is  inserted  in  the  slot  a  central 
portion  only  of  the  lens  is  illuminated.  This  can  be  easily  seen 
by  breathing  upon  the  lens  surface.  It  should  be  accurately 
measured,  and  this  area  will  be  the  true  working  aperture  of  the 
lens  with  the  diaphragm  used.  This  area  of  illumination  will 
be  found  to  differ  in  geometrical  proportion  with  each  separate 
diaphragm. 

Aplanatic.  A  term  applied  to  a  lens  to  denote  that  spherical 
and  chromatic  aberration  have  been  totally  eliminated  so  far  as 
is  practicable;  it  is  impossible  to  do  it  theoretically.  Rays  of 
light  diverging  from  a  point  parallel  to  the  axis  of  an  aplanatic 
lens  passing  through  it,  though  suffering  refraction,  are  brought 
to  a  definite  focus  at  a  point  which  is  the  true  focus  of  a  lens. 
Practically  it  means  that  a  lens  will  give  reasonably  sharp 
definition  with  its  full  aperture. 

Apparatus.  The  materials  used  in  producing  photographs, 
such  as  lens,  camera,  stand,  slides,  etc.,  which  will  be  severally 
described  under  their  various  headings. 

Aqua  Fortis.   See  Nitric  Acid. 

Aqua  Regia.    See  Nitro-Hydrochloric  Acid. 

Arabic  Gum.   See  Gum  Arabic. 

Architectural  Photography.  Specialisation  in  photographic 
work  will  often  repay  an  amateur  far  more  than  the  mere  taking 
of  anything  and  everything  that  he  may  come  across,  and  which 
looks  pretty.  Architectural  photography,  if  taken  up  as  a  special 
study,  will  well  repay  any  one  ;  but  it  is  first  necessary,  to  do  this 
intelligently,  that  he  should  have  some  knowledge  of  the  various 
styles  of  architecture.    The  best  books  of  moderate  price  upon 

26 


DICTIONARY  OF  PHOTOGRAPHY.  [ArC 

this  subject  are  "An  Introduction  to  Gothic  Architecture,"  by 
J.  H.  Parker,  price  5s.,  and  "A  Concise  Glossary  of  Architecture," 
price  Js.  6d.  For  this  particular  branch  of  our  art  a  square 
bellows  camera  is  required.  This  form  is  preferable  to  the 
conical  as  being  somewhat  more  rigid,  and  there  being  no 
chance  of  the  bellows  cutting  off  any  portion  of  the  subject. 
The  size  of  the  camera  will  of  course  depend  entirely  upon 
individual  tastes.  The  lenses  must  be  doublets,  and  at  least 
three  should  be  obtained — a  short-focus,  embracing  an  angle  of 
at  least  750;  a  medium-angle,  about  the  same  focal  length  as 
the  base  of  the  plate,  and  a  longer  focus,  which  should  be  half 
as  long  again  as  the  base  line  of  plate.  All  should  fit  the  same 
flange,  or  adapters  should  be  obtained.  Possibly  the  most 
convenient  sets  of  lenses  will  be  found  in  the  so-called  M  Casket 
Lenses,"  which  consist  of  various  combinations  of  varying  foci, 
which  screw  into  a  tube  forming  doublets  of  the  ordinary  type 
varying  in  foci  from  very  short  to  long.  A  plumb  and  level 
must  be  attached  to  the  camera,  and  the  camera  back  must 
swing  from  the  centre.  The  stand  should  be  firm  and  solid,  and 
the  tips  of  the  legs  should  be  provided  with  cork  bungs  or 
indiarubber  pads  to  prevent  slipping  on  stone  or  marble  floors. 
Equipped  as  above  it  will  be  possible  to  tackle  almost  every 
branch  of  architectural  work,  and  by  using  one  only  of  the 
combinations  of  above  lenses  we  may  obtain  lenses  of  still 
greater  focus.  It  is  true  that  these  will  be  single  lenses,  and 
therefore  liable  to  give  marginal  distortion,  but  really  this  may 
be  ignored  as  only  the  centre  of  the  field  is  used  ;  in  fact,  when 
a  single  lens  is  the  sole  instrument  which  a  worker  has,  let  him 
not  hesitate  to  boldly  attack  architectural  studies,  and  no  one 
will  be  the  wiser,  if  the  lens  is  not  strained  by  raising  the  front, 
or  the  swing  back  abnormally  used.  Finally,  we  may  dismiss 
all  further  reference  to  lenses,  with  the  parting  advice  to  use 
as  long  a  focus  one  as  the  situation  of  the  object  will  allow. 
Obviously,  we  cannot  think  for  one  moment  of  including  directions 
as  to  the  best  time  of  day,  position,  etc.,  of  taking  buildings, 
churches,  etc.,  but  a  few  hints  may  be  acceptable.  Never  take 
a  church  or  house  full  face,  nor  with  the  sun  dead  behind  the 
camera  nor  dead  in  front ;  try  to  get  a  side  or  corner  view  and 
side  lighting.  In  all  church  or  cathedral  exteriors,  where  fine 
delicate  carving  or  tracery  exists,  a  somewhat  long  exposure 

27 


Are] 


DICTIONARY  OF  PHOTOGRAPHY. 


should  be  given  in  order  not  to  lose  the  same.  For  interior 
work  there  is  one  absolute  essential,  and  that  is  that  thickly 
coated  plates,  backed,  should  be  used.  No  plate  that  is  not 
backed  will  give  perfect  results  ;  for  not  only  is  halation  more 
troublesome,  but  also  the  negatives  as  a  rule  are  less  brilliant. 
When  unbacked  plates  are  used,  the  rapidity  of  the  plate  is 
really  of  no  moment  provided  one  can  give  long  exposures  ;  but 
if  from  any  cause  this  is  impossible,  then  the  most  rapid  plates 
attainable  should  be  employed.  We  may  add  here  that  colour- 
sensitive  plates  are  decidedly  to  be  preferred,  and  that  the  new 
multiple-film  plate  introduced  by  R.  W.  Thomas  &  Co.,  will  be 
found  of  great  value  for  all  architectural  work,  especially  interiors. 
The  aperture  of  the  lens  should  always  be  the  largest  that  will 
give  satisfactory  definition  over  the  whole  of  the  screen.  Never 
place  the  camera  exactly  in  the  centre,  rather  a  little  to  one 
side,  of  a  church  or  cathedral.  The  question  of  exposure  is 
always  an  extremely  difficult  one,  and,  whilst  experience  is 
invaluable,  some  such  guide  as  an  actinometer  or  exposure 
meter,  which  actually  gauges  the  chemical  activity  of  the  light, 
will  be  of  immense  advantage.  To  correctly  judge  the  exposure 
for  interiors,  especially  if  there  is  much  coloured  glass  about, 
without  some  such  guide  is  an  utter  impossibility.  By  far  the 
best  light  to  choose  for  exposure  is,  for  the  east  end,  the 
afternoon,  for  the  west  end  the  morning,  and  never  in  sunshine : 
diffused  light  is  far  superior  and  less  likely  to  give  rise  to 
halation.  With  regard  to  development,  thin  delicate  negatives 
are  the  most  suitable,  and  the  newer  developing  agents,  amidol 
and  metol,  will  be  found  of  great  value,  and  far  superior  to 
pyro.  If  records  and  not  pictures  of  architectural  subjects  are 
desired,  then  it  is  wise  to  include  in  the  view  a  two-foot  rule 
which  shall  show  the  scale  on  which  the  object  is  taken  ;  and 
the  plane  of  the  plate  should  be  parallel  to  the  plane  of  the 
wall  or  surface  of  the  building. 

Area  System  of  marking  Lenses  and  Diaphragms.  This 
was  proposed  by  Mr.  George  Smith  to  replace  the  existing 
methods  of  marking  stops.  It  is  not  so  simple  and  has  never 
come  into  general  use.  The  actual  method,  as  described  by  the 
inventor,  is  to  measure  the  aperture  of  stop  in  sixty-fourths  of  an 
inch.    This  number  is  squared ;  the  product  is  the  exact  area  of 

28 


DICTIONARY  OF  PHOTOGRAPHY. 


[Art 


the  aperture  in  circles,  each  one  sixty-fourth  of  an  inch  in 
diameter.  Thus,  supposing  a  stop  aperture  measured  20  sixty- 
fourths,  20  x  20  =  400,  the  last  figure  is  struck  off  and  the  stop 
called  No.  40,  no  matter  what  focus  lens  was  used.  Any  lens 
is  measured  for  its  actual  focus  by  measuring  the  distance  of  its 
burning  point  from  the  back  of  the  lens  in  complete  quarter- 
inches  neglecting  fractions.  Suppose  a  lens  was  found  to 
measure  20  quarter-inches  ;  20  x  20  =  400,  striking  off  the  last 
figure,  its  area  number  would  be  40.  Any  other  lens  would  be 
measured  in  the  same  way  in  quarter-inches.  Thus  it  will  be 
seen  that  every  stop  has  its  own  number,  and  that  whatever 
relation  that  number  has  to  that  of  the  lens  it  is  used  with  gives 
at  a  glance  the  exposure  required.  It  need  hardly  be  pointed 
out  that  this  method  is  full  of  grave  inaccuracies. 

Argentometer.  An  instrument  constructed  on  the  principle 
of  a  Hydrometer  (q.v.),  and  marked  with  a  scale  to  show  the 
number  of  grains  per  oz.  of  nitrate  of  silver  in  a  silver  bath. 
This  is,  of  course,  only  applicable  when  the  solution  is  pure. 

Argentotype.  A  name  applied  to  one  particular  make  of 
gelatino-bromide  paper. 

Aristogen.  Under  this  name  Liesegang  has  introduced  a 
concentrated  hydroquinone  developer,  specially  designed  for 
developing  gelatino-chloride  prints.    Its  formula  is  said  to  be 

Hydroquinone  (10%  alcoholic  sol.)         ...      10  parts. 
Sodium  sulphite  cone.  sol.  ...       ...      10  ,, 

,,      acetate  20%  sol.    ...       ...       ...       5  ,, 

Citric  acid,  20%  sol.  ...       ...       ...       5  ,, 

Water    100  „ 

Aristotype.  A  name  applied  to  one  particular  make  of 
gelatino-chloride  paper. 

Arrowroot  (Ger.,  Pfcihvarzclmchl ;  Fr.,  andjltal.,  Arrowroot). 
The  starch  obtained  from  the  tubers  of  Maranta  Arundinacea. 
It  is  a  fine,  white,  tasteless,  odourless  powder  which  has  a  parti- 
cular crepitating  feel  in  bulk.  It  is  used  for  sizing  papers  in  the 
platinotype  and  plain-paper  processes. 

Artotype.    See  Collotype. 

29 


Asp]  DICTIONARY  OF  PHOTOGRAPHY. 

Asphalt  (Ger„  Asphalt,  Judenpech ;  Fr.,t  Bitume  de  Judec, 
Asphalte;  Ital.,  Bitume  di  Giudea,  Asfaltd).  Synonym  :  Bitumen, 
Jews'  pitch.  It  is  met  with  in  commerce  in  black  or  brown  lumps 
of  peculiar  gassy  and  tarry  odour,  and  is  obtained  from  Judea 
Syria,  Trinidad,  and  other  places.  Syrian  bitumen  is  the  one 
most  generally  used  in  photography  as  it  contains  52  per  cent,  of 
the  light-sensitive  preparation.  It  is  prepared  for  photographic 
purposes  by  three  different  methods  :  (1)  Solution  of  the  asphalt 
in  chloroform  and  precipitation  with  from  three  to  five  times  the 
quantity  of  ether.  (2)  Kayser's  method  of  washing  powdered 
raw  asphalt  with  ether,  and  using  the  dried  marc  for  the  prepara- 
tion of  the  light-sensitive  varnish.  (3)  Husnik's  method  of 
dissolving  raw  asphalt  in  the  smallest  quantity  possible  of 
German  turpentine  and  precipitating  with  several  times  the 
quantity  of  ether.  Kayser  proved  that  the  light-sensitiveness 
of  asphalt  increased  with  the  proportion  of  sulphur,  and  Valenta 
based  the  following  processes  of  increasing  the  sensitiveness  on 
this  statement.  To  prepare  the  light-sensitive  preparation  7  to  10 
parts  of  sulphur  should  be  dissolved  in  a  sufficient  quantity  of 
bisulphide  of  carbon,  and  added  to  100  parts  of  powdered  Syrian 
asphalt.  The  solution  is  then  freed  from  the  bisulphide  of 
carbon  as  described,  and  best  heated  for  about  an  hour  in  a 
mortar  to  iio°C,  with  constant  attrition  with  the  pestle;  then 
in  a  roomy  air-bath  slowly  heated  till  sulphuretted  hydrogen 
escapes,  and  be  kept  at  a  temperature  of  about  1800  to  2000 
C.  for  5  to  6  hours.  The  formation  of  burnt  products,  which 
prove  a  decomposition  of  the  asphalt,  are  caused  by  too  high  a 
temperature,  and  is  to  be  avoided.  The  asphalt  thus  prepared, 
which  now  only  smells  faintly  of  sulphuretted  hydrogen,  should 
be  kept  in  a  well-closed  bottle  in  the  dark.  For  working  in 
diffused  daylight,  and  especially  if  high  sensitiveness  is  desired, 
it  is  advisable  to  free  this  asphalt  from  any  existent  resin,  and 
from  traces  of  burnt  products,  which  may  be  effected  by  powder- 
ing and  treating  the  powder  with  ether,  and  with  agitation  in  a 
wide-mouthed  bottle  fitted  with  a  cork.  After  sufficient  action, 
2  to  3  hours,  the  ether  is  poured  off  and  the  insoluble  portion  dried 
by  spreading  it  out  in  thin  layers  on  several  thicknesses  of  blotting 
paper.  For  use,  four  parts  of  sulphurised  asphalt,  treated  as 
above,  are  to  be  dissolved  in  100  parts  of  benzol  (not  benzine), 
the  solution  filtered,  and  [finally  diluted  till  the  film  which  is 

39 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ast 


formed  by  pouring  it  on  the  zinc  plate  appears  a  golden-yellow 
colour.  (An  exposure  of  from  half-an-hour  to  one  hour  of  the 
solution  of  asphalt  in  an  open  flask  to  direct  sunlight  is  advis- 
able.) To  develop  the  asphalt  pictures  rectified  oil  of  turpentine 
free  from  acid,  the  most  suitable  French  or  Austrian  turpentine, 
should  be  used.  As  accelerator  of  development  with  strong  over- 
exposure, an  addition  of  so-called^Russian  or  Hungarian  turpentine 
may  be  made,  which  oils,  when  used  alone,  would  attack  the 
image.  As  restrainer  in  developing,  an  addition  of  ligroin,  benzine 
(petroleum  benzine),  or  wood  oil  may  be  used.  The  development 
is  best  effected  by  merely  rocking  in  a  dish  without  the  help  of 
any  pad  of  cotton  wool ;  and  soon,  when  the  image  is  developed 
clear,  it  should  be  well  washed  in  a  stream  of  water  and  allowed 
to  drain  and  dry.  (In  order  to  avoid  the  unpleasant  action  of  ad- 
hering drops  of  water,  the  plate  may  be  washed  with  petroleum 
benzine  before  washing  with  water.)  It  is  advantageous  before 
gumming  the  plate  to  expose  it,  as  the  image  adheres  better. 
Valenta  also  suggests  the  following  simplified  method  of  preparing 
light-sensitive  sulphurised  asphalt  or  bitumen  : — 100  grammes  of 
raw  Syrian  asphalt  are  to  be  boiled  with  an  equal  quantity  of 
commercial  pseudo-cymene  in  which  12  grammes  of  sulphur 
flowers  have  been  dissolved.  When,  after  about  three  or  four 
hours,  the  formation  of  sulphuretted  hydrogen  has  ceased,  the 
cymene  is  distilled  off,  andthe  product  is  the  light-sensitive  asphalt 
from  which  the  film  is  prepared  in  the  usual  way  by  solution  in 
benzol.  The  new  preparation  is  soluble  in  benzol,  toluol,  cymene, 
xylol,  and  turpentine  ;  it  is  said  to  be  even  more  sensitive  than 
that  prepared  by  Valenta's  other  method.  Bitumen  is  used  in 
several  photomechanical  processes  for  making  a  light-sensitive 
film,  and  raw  bitumen  for  laying  the  ground  in  photogravure. 

Astigmatism.  A  defect  in  lenses  from  which  vertical  and 
horizontal  lines  near  the  margin  of  the  field  cannot  be  both 
accurately  focussed  at  the  same  time.  It  is  particularly  notice- 
able with  lenses  of  large  aperture,  and  is  cured  to  some  extent 
by  the  use  of  small  diaphragms  or  by  special  selection  of  the 
glass  and  calculation  of  the  curves.  This  should  not  be  con- 
founded with  curvature  of  the  field,  as  in  this  case  the  alteration 
of  the  focus  will  improve  the  same,  though  destroying  the  focus  in 
the  centre.    To  explain  this  we  must  have  recourse  to  a  figure. 

3i 


Ast] 


DICTIONARY  OF  PHOTOGRAPHY. 


If  we  assume  /  o  m  n  to  be  a  convex  lens,  and  a  b  its  axis,  and 
r,r,r,r,r,  rays  proceeding  from  a  point  at  some  distance  from  the 
axis,  and  from  this  point  draw  a  line  R  P,  cutting  the  axis  at  c, 
and  draw  through  this  point,  and  the  principal  axis  of  the  lens,  a 
plane,  the  lens  will  be  cut  by  the  line  /  m.  At  right  angles  to  this 
we  draw  the  plane  o  n,  through  which  the  plane  of  rays,  r",r,r", 


jP 


Fig.  4. 

shall  pass.  We  shall  mow  see  that  the  rays  passing  through 
0  c  n  will  meet  at  the  point  p,  but  the  rays,  r',  r',  passing  through 
/  m  will  cut  the  axis  R  p  at  0.  If  we  assume  that  we  have  two 
straight  lines  as  in  fig.  5  to  reproduce  at  the  margins  of  the  focus- 
sing screen,  we  shall  find  that  we  can  at  the  point  p  obtain  an 
image  of  b  b  every  point  of  which  is  slightly  lengthened,  and  can  be 
represented  as  in  fig.  5  d,  whilst  the  upright  line  a  a  will  be  repre- 

32 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ast 


sented  by  c\  <?"  and  appear  as  in  fig.  5  d.  If,  however,  we  focus 
on  a  a,  then  we  shall  obtain  a  sharp  image  at  e,  whilst  bb  will  be 
represented  as  in  fig.  5  c.  Some  of  the  later  forms  of  lenses  are  free 


Fig-  5- 

from  astigmatism  over  a  certain  field,  notably  the  Anastigmats  of 
Zeiss  and  Goerz.  In  the  old  form  of  lenses  the  optician  has  to 
make  a  compromise  between  curvature  of  the  field  and  astigma- 


Fig.  6. 


tism  ;  and  the  best  lenses  are  those  which  represent  a  point  as  a 
somewhat  thickened  star.  In  focussing  a  line  at  p,  fig.  4,  and 
racking  the  lens  in  to  o,  it  goes  through  the  shapes  shown 
in  fig.  6. 

Astronomical  Photography.  This  is  practically  beyond  the 
reach  of  the  ordinary  worker,  as  the  size  of  the  images  given  by 
ordinary  photographic  lenses  is  excessively  small,  being,  in  the 
case  of  the  sun  or  moon,  ^  of  an  inch  in  diameter  for  every  ten 
inches  of  focus,  but  with  Dallmeyer's  telephotographic  lenses 
considerable  augmentation  of  the  size  is  obtained  ;  on  the  other 
hand,  when  it  is  desired  to  obtain  negatives  of  any  portion  of  the 
sky,  portrait  lenses  of  about  6  inches  aperture  and  30  inches  focus 
may  be  used  for  half  or  whole  plates,  which  will  give  fairly 

33  P 


Aur]  DICTIONARY  OF  PHOTOGRAPHY. 

successful  results.  The  most  useful  article  on  this  subject  will 
be  found  in  Astronomy  and  Astrophysics,  October  1892,  p.  641. 
Possessors  of  a  i\  or  3-inch  refracting  telescope  may,  however, 
wish  to  utilise  the  same  for  lunar  or  stellar  work,  and  in  such  a 
case  it  is  necessary  to  remove  the  eye-piece,  and  attach  a  very 
light  camera  in  its  place,  the  operation  of  focussing  and  exposing 
being  the  same  as  usual,  using  very  rapid  plates,  and  giving 
exposures  of  about  \  or  \  sec. ;  longer  than  this  will  cause  blur- 
ring of  the  image,  due  to  the  combined  movements  of  the  earth 
and  moon.  As  astronomical  telescopes  are  corrected  for  the 
visual  and  not  the  chemical  rays,  it  is  necessary  to  find  out 
experimentally  the  difference  ;  and  this  is  best  done  by  focussing 
with  the  eye  as  sharply  as  possible,  and  then  racking  the  plane 
of  the  sensitive  surface  further  out  by  sixteenths  of  an  inch, 
making  an  exposure  after  each  movement  till  the  sharpest  image 
is  obtained  on  the  negative  after  development.  The  distance 
thus  found  may  be  once  for  all  marked  on  the  draw-tube  of  the 
telescope. 

Aurantia  (Ger.,  Aurantia ; -  Ft.,  Aurantia  ;  Ital.,  Auranzid). 
N(C6H2[N02]3)2NH4  is  formed  by  the  nitrification  of  Dipheny- 
lamin.  The  commercial  preparation  contains  numerous  im- 
purities insoluble  in  alcohol,  but  the  pure  dye  is  easily  soluble 
in  alcohol,  is  not  destroyed  by  acids,  and  with  alkalies  turns 
more  reddish.  It  has  been  used  in  orthochromatic  photography 
not  only  for  sensitising  plates  but  also  for  the  preparation  of  the 
coloured  Screens  (q.v.~),  and  in  the  preparation  of  a  secret  solution 
called  Nuktigonia,  which  has  been  recommended  as  an  addition 
to  developers,  so  that  plates  could  be  developed  in  ordinary 
rooms  without  fogging.  The  formula  of  such  a  preparation  is  as 
follows : — 

Aurantia    16  parts. 

Carmine      ...       ...       ...       ...       ...       8    ,,  • 

Water    24  „ 

Alcohol    24  „ 

Add  sufficient  ammonia  to  effect  complete  solution.  Six  parts 
of  this  to  be  added  to  every  100  of  developer.  Its  use,  we  need 
scarcely  add,  is  not  to  be  commended. 

Aurine  (Ger.,  Aurm;  Fr.,  Anrine ;  Ital.,  Aurina).  Cl9H,40;v 

34 


DICTIONARY  OF  PHOTOGRAPHY. 


[Aux 


Synonyms:  Rosolic  acid,  Yellow  coralline.  This  is  a  dark, 
amorphous  mass  of  reddish-green,  iridescent  tinge,  formed  by 
the  treatment  of  carbolic  acid  with  acids,  etc.  It  is  insoluble  in 
water,  but  soluble  in  spirit  and  ether,  which  it  colours  yellow. 
It  has  been  suggested  to  make  non-actinic  leather  collodion, 
which  should  be  spread  on  the  back  of  dry  plates  to  prevent 
halation. 

Autogravure.  A  term  applied  to  prints  obtained  by  the 
Photogravure  process  (q.v.). 

Automatic  Photography.  Several  machines  have  been  in- 
vented, consisting  of  a  series  of  wheels  and  levers,  which  are 
set  in  motion  by  dropping  a  coin  in  a  slot,  which  are  supposed 
to  turn  out  perfect  photographs.  We  need  hardly  point  out  that 
it  is  difficult  to  replace  brains  and  thinking  powers  by  any  clock- 
work arrangement. 

Autotype  Process.   See  Carbon  Process. 

Auxiliary  Exposure.  It  is  needless  to  state  that  a  definite 
exposure  is  necessary  to  obtain  any  light  action.  When,  from 
certain  circumstances,  the  exposure  is  too  short  to  allow  of  the 
whole  Of  the  image,  particularly  in  the  shadows,  affecting  the 
film,  it  has  been  stated  that  an  auxiliary  exposure  is  of  great 
assistance.  The  auxiliary  exposure  may  be  either  preliminary 
to  or  after  the  real  exposure.  In  the  old  daguerreotype  days 
it  was  sometimes  customary  to  expose  the  plate,  after  the  real 
exposure  had  been  given,  to  the  light  passing  through  red  or 
yellow  glass,  and  a  more  fully  exposed  image  was  obtained. 
With  the  wet-plate  process  it  was  warmly  upheld  by  several 
experts.  With  gelatino-bromide  plates,  in  consequence  of  their 
rapidity,  the  auxiliary  exposure  is  so  extremely  short  that  in- 
dubitable proof  of  its  advantage  is  hard  to  obtain.  A  method 
suggested,  and  which  has  certainly  the  merit  of  simplicity  to 
recommend  it,  is  to  replace  the  ordinary  lens  cap  with  a  flap 
shutter,  the  inside  of  which  is  a  sheet  of  pale  yellow  glass,  ground 
on  one  side.  The  shutter  is  so  arranged  that  the  glass  and  flap 
can  be  lifted  together  to  give  the  true  exposure  ;  and,  when  this 
is  completed,  the  shutter  alone  is  lifted,  leaving  the  yellow  glass 
covering  the  lens,  and  a  flash  as  quick  as  possible  is  given 

35 


Axi] 


DICTIONARY  OF  PHOTOGRAPHY. 


through  this.  It  is  only  fair  to  add  that  the  benefit  of  an  auxiliary 
exposure  with  dry  plates  is  much  disputed,  and  possibly  because 
it  has  to  be  so  short,  or  else  general  fog  supervenes.  The 
rationale  of  auxiliary  exposure  is  that  it  either  commences 
the  necessary  chemical  action,  or  else  adds  to  the  action 
already  commenced  by  the  true  exposure,  and  thus  gives  a 
developable  image,  or  one  which  develops  easier.  Auxiliary 
exposure  has  also  been  suggested  for  printing  processes, 
and  with  regard  to  gelatino-chloride  paper  there  is  no  doubt 
that  a  preliminary  exposure  to  white  light  prevents  loss 
of  detail  in  the  high  lights  in  the  processes  of  toning  and 
fixing. 

Axis.  The  axis  of  a  lens  is  the  imaginary  straight  line  which 
passes  through  the  optical  centre  of  the  lens.  The  principal  axis 
passes  through  the  centre  of  the  radius  of  curvature  and  the 
optical  centre  ;  any  other  straight  line  passing  through  the  optical 
centre  is  termed  a  secondary  axis. 

Azaline.  This  is  a  mixture  of  quinoline,  or  chinoline,  red  and 
quinoline  blue,  or  cyanin,  in  the  proportion  of  10  parts  of  the 
former  to  I  part  of  the  latter  dissolved  in  iooo  parts  of  alcohol, 
and,  when  mixed  with  ammonia  and  water,  is  used  in  ortho- 
chromatic  photography  to  sensitise  plates  for  red  and  yellow. 
The  actual  bath  is  prepared  as  follows : — 

Azaline  solution,  as  above   4  parts. 

Liq.  ammonia    1 

Alcohol     30 

Water   70  „ 

Background.  Anything  used,  as  the  name  implies,  as  sub- 
ordinate to  or  behind  the  principal  figure  or  figures  or  objects  in 
a  photograph.  There  are  many  kinds — natural,  artificial,  in- 
teriors, exteriors,  or  plain.  Natural  backgrounds  when  properly 
used  are  the  most  pleasing,  and  as  these  cannot  be  made  to 
order,  the  intelligent  amateur  will  choose  his  own.  The  artificial 
background  is  too  well  known  from  the  work  of  the  professional 
to  need  much  description.  A  pleasing  plain  background  can  be 
made  with  a  workhouse  or  dark  brown  blanket,  or  with  one  of 
the  ordinary  kind.     An  ordinary  white  sheet,  or  even  brown 

36 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bac 


paper  of  the  kind  used  for  placing  under  carpets,  may  be  pressed 
into  service  in  place  of  better  material.  The  following  directions 
for  making  a  movable  background  may  be  of  service  to  some : — 
Make  a  frame  of  inch  deal  6  ft.  high  and  4  ft.  6  ins.  wide.  It  can 
be  made  to  take  to  pieces  by  using  iron  pins  at  the  corners.  At 
the  top  have  two  projecting  iron  rods,  about  4  ft.  long,  at  an  angle 
of  135°  This  to  be  made  extendable  at  will.  Side-shades 
should  be  made  in  the  same  manner.  Unbleached  calico  can 
be  used,  which  should  be  freely  painted  over  with  the  following 
distemper : — 

Common  whiting     ...       ...       ...       ...  1  lb. 

Glue  powder...    ...       ...  j  ,, 

Treacle    $  pint. 

Water    }  gall. 

Mix  the  above  thoroughly,  and  add 

Ivory  black   1  oz. 

Ultramarine  ...       ...       ...       ...       ...       \  ,, 

Red  ochre     ...       ...       ...       ...       ...       }  ,, 

ground  down  into  a  very  fine  cream  with  water.  It  can  be 
darkened  or  lightened  according  to  amount  of  colour  added  ;  the 
colour  is  lighter  when  dry.  Some  of  the  most  artistic  results  are 
to  be  obtained  by  the  use  of  graduated  or  shaded  backgrounds  ; 
these,  though  somewhat  difficult  to  successfully  make  at  home, 
may  be  obtained  at  a  very  reasonable  price  from  nearly  all 
dealers. 

Backing  Plates  consists  of  coating  the  back  of  plates  with 
some  black  or  non-actinic  substance  to  prevent  Halation  (q.v.). 
The  essentials  of  a  perfect  backing  are  that  it  should  reflect 
no  rays  of  light — or,  at  least,  only  those  that  are  non-actinic — 
and  that  it  should  be  in  absolute  optical  contact  with  the  back 
of  plate.  Several  methods  have  been  recommended,  coating 
the  back  of  the  plate  with  collodion  stained  with  aurin  or  any 
non-actinic  dye  being  a  method  which  is  easier  advised  than 
done  in  the  dim  light  of  the  dark-room.  The  following,  if 
spread  upon  brown  paper  and  damped  before  applying  to  the 
plate,  answers  well :  — 

37 


Bal] 


DICTIONARY  OF  PHOTOGRAPHY. 


Powdered  burnt  sienna 

Gum  

Glycerine 

Water  

Or 

Gelatine       ...       ...       ...       ...       ...      50  grs. 

Glycerine     ...       ...       ...       ...       ...       £  oz. 

Water    1  ,, 

Indian  ink  or  ivory  black   30  grs. 

Whatever  backing  is  used,  it  must  be  removed  before  develop- 
ing. Debenham  has  suggested  the  use  of  caramel  or  burnt  sugar 
and  sienna ;  it  has  been  found  to  be  the  most  effective  and 
easily  prepared  of  any,  and  is  made  with 

Mucilage    1  oz. 

Caramel    I 

Sienna  in  powder    ...       ...       ...       ...       1  „ 

Mix  in  a  mortar ;  distribute  this  over  the  back  of  the  plate  with 
a  roller  squeegee  or  pad  of  lint.  Cornu  recommends  a  mixture 
of  6  parts  of  oil  of  cloves,  and  1  part  of  oil  of  turpentine  made 
into  a  paste  with  lampblack. 

Balance.  A  term  used  in  composition  to  denote  the  proper 
relation  of  lines  and  lights  and  shadows,  so  as  to  secure  harmo- 
nious and  symmetrical  pictures.  The  subject  is  much  too  com- 
prehensive to  treat  of  here,  H.  P.  Robinson's  11  Pictorial  Effect  in 
Photography  "  being  the  best  guide  on  the  subject. 

Balloon  Photography.  As  early  as  1858  Nadar  of  Paris 
obtained  a  photograph  of  the  earth  below  from  the  car  of  a  balloon, 
and  during  the  American  war  of  186 1-2,  photography  from  balloons 
was  practically  applied  to  warfare.  Since  that  date  numerous 
experiments  have  been  made,  both  with  captive  and  free  balloons, 
to  obtain  results  which  might  be  of  value  in  warfare.  The 
attempts  have  proved  that  such  work  is  not  only  possible,  but 
might  be  of  value. 

Barium  Bromide  (Ger.,  Baryum  bromid;  Ft.,  Bromure  de 
baryum  ;  Ital.,  Bromuro  di  bario).  BaBr22H20  =  333.  Prepared 
by  neutralising  hydrobromic  acid  with  barium  carbonate.  Solu- 

3« 


10  ozs. 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bar 


bility  :  100  parts  are  soluble  in  96  parts  of  cold  water,  and  in  75 
parts  boiling ;  it  is  also  soluble  in  alcohol  and  ether.  Occasionally 
used  in  collodion.    It  is  poisonous. 

Barium  Chloride  (Ger.,  Bariumchlorid  or  Chlorbarium  ;  Fr., 
Chlorure  de  baryum  ;  Ital.,  Cloruro  di  bario).  BaCL2H20  =  244. 
Prepared  by  heating  barium  carbonate  with  hydrochloric  acid,  or 
by  heating  in  a  reverberatory  furnace,  powdered  heavy  spar 
(BaS04),  calcium  chloride,  chalk  and  coal  dust,  extracting  the 
chloride  of  barium  with  water,  and  crystallising.  It  occurs  as 
white  tabular  crystals,  permanent  in  air,  which  lose  their  water 
of  crystallisation  at  1500.  It  is  poisonous.  It  is  occasionally 
employed  in  salting  albumenised  paper,  and  for  making  Baryta 
Paper  (q.v.)  and  imitation  opal  glass.  Solubility  :  36  per  cent, 
in  cold,  59  per  cent,  in  boiling  water ;  0  01  per  cent,  in  cold 
alcohol,  0-5  per  cent,  in  hot  alcohol,  10  per  cent,  in  glycerine. 

Barium  Iodide  (Ger.,  Iodbariunt;  Fr.,  Iodure  dc  baryum; 
Ital.,  Ioduro  di  bario).  Bal2==39i.  Prepared  by  heating  iron 
filings  and  iodine  till  colourless  or  pale  yellowish  green,  then 
adding  barium  hydroxide  as  long  as  a  precipitate  is  formed, 
filtering  and  evaporating.  It  occurs  in  deliquescent  tabular 
crystals.  Solubility  :  1  in  -48  of  cold,  and  1  in  -35  of  hot  water  ; 
soluble  in  spirit,  and  slightly  so  in  ether.    Used  in  collodion. 

Barium  Nitrate  (Ger.,  Bariumnitrat ;  Fr.,  Azotatc  dc 
baryum;  Ital.,  Azotato  di  barite).  Ba  (N03)2  =  261.  Pre- 
pared by  neutralising  dilute  nitric  acid  with  barium  carbonate, 
evaporating  and  crystallising.  It  occurs  in  octahedral  translucent 
crystals.  Solubility:  8  per  cent,  in  cold,  35  per  cent,  in  hot 
water ;  insoluble  in  alcohol.  It  is  poisonous.  Used  to  prepare 
ferrous  nitrate — a  developer  for  the  wet-plate  process.  It  is  also 
recommended  as  an  addition  to  the  silver  bath  to  prevent  the 
formation  of  pin-holes,  and  has  been  suggested  as  an  ingredient 
in  Magnesium  Flash-light  (q.v.). 

Barium  Sulphate  (Ger.,  Bariumsulfat,  or  Schtvcrspath  ; 
Fr.,  Sulfate  dc  baryum;  Ital.,  Solfato  bi  barite).  BaS04. 
Synonym  :  Heavy  spar,  Blanc  fixe,  Mountain  snow.  Only 
used  in  the  form  of  an  emulsion  to  prepare  baryta  paper  and 
imitation  opal  glass. 

Baryta  Paper  (Ger.,  Kreide-papier,  or  Baryt-papicr ;  Fr. 
39 


Bat] 


DICTIONARY  OF  PHOTOGRAPHY. 


Baryte  papier).  Paper  coated  with  an  emulsion  of  sulphate  of 
barium  and  chrome  alum,  which  is  used  as  a  support  for  gelatino- 
chloride  printing-out  emulsions  and  for  collotype  printing,  etc. 
A  formula  for  its  preparation  is  the  following : — 

I. 

  9°  §rs- 

  30  M 

  5  ozs. 

II. 

Ammonium  sulphate    15  grs. 

Distilled  water    2%  ozs. 

Soak  the  gelatine  in  the  water  till  soft,  add  the  barium,  and 
dissolve  by  heat;  then  add  solution  II.  in  small  quantities, 
shaking  between  each  addition ;  allow  the  emulsion  to  set ; 
break  up  into  small  pieces ;  wash  thoroughly,  and  add  7^  grains 
of  chrome  alum  previously  dissolved  in  a  little  water. 

Bath.  This  term  is  used  indiscriminately  to  describe  dishes 
and  other  vessels,  and  also  the  liquids  which  are  used  in  the 
same.  The  vessels  are  made  of  various .  materials,  such  as 
porcelain,  glass,  ebonite,  celluloid,  etc.  The  only  term  which 
requires  explanation  in  connection  with  the  liquids  is  that  which 
is  frequently  used  when  speaking  of  the  strength  of  the  same  :  it 
is  customary  to  say,  "  a  60,  50,  or  48,  etc.,  grain  bath  " — this 
means  that  60,  50,  or  48  grains  of  any  chemical  are  contained 
in  every  ounce  of  the  liquid. 

Beach's  Developer.  Named  after  its  inventor,  Mr.  F.  C. 
Beach,  of  New  York.  It  is  rather  complicated  in  formula,  but 
has  been  widely  used.    It  is  made  as  follows  : — 

Pyro  Solution. 
Hot  distilled  water          ...       2  ozs.  or  59  c.cm. 
Sulphite  of  soda    2  ozs.  ,,  62  grms. 

When  cold  add 

Sulphurous  acid    ...       ...       2  ozs.  or  59  c.cm. 

Pyrogallol   ...       ...       ...       \  oz.       15*5  grms. 

40 


Gelatine,  Heinrich's 
Barium  chloride 
Distilled  water 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ben 


Potash  Solution. 
Carbonate  of  potash        ...       3  ozs.  or  93-3  grms. 

Sulphite  of  soda   2   ,,    ,,     62  ,, 

Water    7   ,,        207  c.cm. 

Dissolve  the  salts  separately  and  mix.  For  a  plate  having  the 
normal  exposure,  mix  the  pyro  and  potash  solutions  in  equal 
proportions,  using  1  dram  of  each  to  every  1  oz.  of  water ;  for 
under-exposure,  use  more  of  the  potash  solution,  and  vice 
versa. 

Beechey's  Emulsion  Process.   See  Collodion. 

Beeswax  (Ger.,  Wachs ;  Fr.,  Cire ;  Ital.,  Cera;  Lat.,  Cera 
Havd).  This  is  obtained  from  the  honeycomb  of  the  bee,  and  is 
a  yellow  mass  breaking  with  a  granular  structure  and  of  pleasant 
smell.  It  should  be  entirely  soluble  in  hot  oil  of  turpentine,  and 
is  insoluble  in  alcohol  and  water.  White  wax  is  the  above 
bleached  by  exposure  to  air  and  light,  and  cast  into  flat  round 
cakes. 

Bellows.  In  all  forms  of  camera  of  the  present  day  that 
portion  which  unites  the  back  and  front  portions  is  called  the 
bellows,  which  are  usually  constructed  of  calico  or  leather.  For 
those  anxious  to  make  their  own  bellows  the  full  description  will 
be  found  in  the  Amateur  Photographer  for  July  10th,  1 891 ,  p.  25. 
There  are  three  principal  varieties  of  bellows  in  the  market  —the 
square,  the  oblong,  and  the  conical.  The  first  entails  most  weight, 
the  second  is  almost  obsolete,  and  the  third  the  most  prevalent 
and  lightest.  The  question  as  to  which  is  the  best  is  purely  a 
matter  of  personal  opinion. 

Benzine  (Ger.,  Benzin;  Fr.,  Be?izine ;  Ital.,  Benzind). 
Synonym :  Benzole.  C6HG  =  78.  A  colourless  liquid,  with 
characteristic  smell  resembling  coal  gas,  obtained  commercially 
by  fractional  distillation  of  coal,  between  360  and  1500  C. ;  it  is 
purified  by  a  second  distillation  at  8o°  C,  and  should  crystallise 
at  o°  C.  It  is  insoluble  in  water,  but  soluble  in  all  proportions 
in  alcohol  and  ether.  It  is  a  solvent  of  all  fixed  and  volatile  oils, 
and  greasy  substances  generally.  It  boils  at  about  85°C,  and  at 
ordinary  temperature  gives  off  a  vapour  which  is  extremely 
explosive.    It  is  used  in  photography  as  a  solvent  in  encaustic 

4i 


DICTIONARY  OF  PHOTOGRAPHY. 


paste,  for  the  preparation  of  matt  varnishes,  and  as  a  developer 
or  solvent  of  bitumen  in  certain  photomechanical  processes. 

Berkeley's  Sulpho-Pyrogallol.   See  Sulpho-Pyrogallol. 

Biconcave.  An  optical  term  denoting  that  the  two  sides  of  a 
lens  are  hollowed  out.    See  Lens. 

Biconvex.  An  optical  term  denoting  that  the  two  sides  of  a 
lens  are  bulged  out.    See  Lens. 

Binocular  Camera.  Another  name  for  Stereoscopic  Camera 
{q.v.). 

Bitumen.    See  Asphalt. 

Blacking.  The  interior  of  all  cameras,  dark  slides,  and  lens 
tubes  should  be  coated  with  a  dead  black  to  prevent  the  reflec- 
tion of  light  and  subsequent  fog  on  the  plate.  A  good  black 
can  be  made  by  grinding  lamp  or  ivory  black  into  a  paste  with 
japanners'  gold  size.  Another  method  is  by  coating  the  wood, 
etc.,  with  a  solution  of  sulphate  of  iron,  and,  when  dry,  applying 
a  solution  of  tannin  or  decoction  of  logwood,  two  or  three  suc- 
cessive applications  being  sometimes  necessary.  For  blackening 
lens  mounts,  two  or  three  different  methods  are  employed.  Where 
the  mount  will  not  be  touched  by  the  fingers,  drop-black  ground 
up  with  weak  glue  and  water  may  serve,  but  a  better  method 
and  a  more  lasting  one  can  be  made  by  mixing  fine  lampblack 
with  lacquer,  and  applying  it  in  two  or  three  successive  coats  to 
the  heated  mount ;  but  where  the  mount  will  be  fingered,  it  is 
obvious  that  some  other  method  must  be  employed.  We  have 
the  choice  of  two,  one  of  which  results  in  a  bronze  colour,  the 
other  is  an  absolute  dead  black.  For  the  former  colour,  solution 
of  perchloride  of  platinum  acidulated  with  nitric  acid  is  used. 
This  method  is  especially  useful  where  any  soldered  joints 
exist ;  where  solder  is  not  used,  an  absolute  dead  black  can  be 
obtained  by  dipping  the  article,  heated  fairly  hot,  into  a  solution 
of  nitrate  of  copper,  made  by  dissolving  copper  wire  in  dilute 
nitric  acid  ;  it  is  then  heated  over  a  Bunsen  burner  or  spirit 
lamp,  the  green  colour  of  the  copper  first  showing,  and  at  the 
proper  temperature  a  fine  dead  black  appears.  Another  method 
is  to  dissolve  I  part  of  carbonate  of  copper  in  8  parts  of  solution 

42 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bli 


of  ammonia  and  adding  18  parts  of  water.  Clean  the  brass  well 
and  immerse  in  the  solution  till  black,  rinse  with  water,  dry 
in  bran  or  sawdust,  and  give  a  rub  over  with  thin  oil  varnish. 
Another  formula  to  blacken  wood  is  as  follows  : — 


Dissolve  the  extract  in  boiling  water,  add  the  chromate  also  in 
solution.  This  is  a  deep  violet  liquid  which  changes  to  black  in 
contact  with  the  wood.  To  blacken  leather-covered  hand  cameras 
which  have  become  shabby,  the  following  may  be  useful : 

Glue   4  oz. 

Vinegar    l|  pints. 

Gum  arabic  ...       ...       ...       ...       ...       2  oz. 

Black  ink    8  oz. 

Isinglass    2  drm. 

Break  the  glue  in  pieces,  put  in  a  basin,  pour  over  it  about  a 
pint  of  the  vinegar,  let  it  stand  till  it  becomes  perfectly  soft. 
Put  the  gum  in  another  vessel  with  the  ink  until  it  is  perfectly 
dissolved ;  melt  the  isinglass  in  as  much  water  as  will  cover  it, 
which  may  be  easily  done  by  placing  the  cup  near  the  fire  about 
an  hour  before  required  for  use.  To  mix  them,  pour  the  remain- 
ing vinegar  with  the  softened  glue  into  a  vessel  and  heat  on  a 
sand  bath  over  a  gentle  fire  ;  stir  till  dissolved,  and  do  not  let 
heat  be  over  8o3  C.  Add  the  gum  and  heat  to  8o°  C,  add  the 
isinglass,  and  it  is  ready  for  use.  Put  as  much  as  required  in 
a  saucer,  beat  it  till  thin,  and  apply  with  a  small  sponge.  If  the 
article  is  dried  quickly  in  the  sun  or  before  the  fire  it  will  have 
a  better  polish. 

Black  Varnish.   See  Varnish. 

Blanchard's  Brush  consists  of  a  piece  of  swansdown  calico 
doubled  and  fastened  by  means  of  an  indiarubber  band  round  a 
strip  of  glass  2  inches  wide  and  6  inches  long.  It  was  used  for 
coating  plates,  etc.,  with  substratum  for  the  collodion  process. 

Blisters.  One  of  the  worst  troubles  of  an  amateur,  whether 
on  plates  or  paper.    On  the  former,  it  is  usually  the  precursor 


Extract  of  logwood  ... 
Chromate  of  potash 
Water   


30  grs. 
35  ozs. 


I  oz. 


43 


Blu] 


DICTIONARY  OF  PHOTOGRAPHY. 


of  a  general  Frilling  (g.v.).  Blisters  invariably  make  their 
appearance  on  prints,  either  in  the  fixing  bath  or  the  first  washing 
after.  It  is  more  generally  a  fault  with  papers  that  are  heavily 
charged  with  albumen  and  salt,  and  in  this  case  it  is  most 
likely  due  to  exosmose  action  between  the  water  and  the  fixing 
solution,  the  albumen  acting  as  a  septum.  The  remedy  is  to 
plunge  the  prints  immediately  after  fixing  into  a  saturated 
solution  of  salt,  and  use  all  solutions  at  the  same  temperature. 
Blisters  are  frequently  caused  also  by  an  accumulation  of  gas 
behind  the  film  of  albumen,  and  in  this  case  it  would  seem  to . 
be  the  action  of  hypo  upon  a  partially  decomposed  albumen. 
A  cure  for  this  is  to  dip  the  print  on  the  first  sign  of  blistering 
into  a  bath  of  methylated  spirit.  In  the  case  of  some  kinds  of 
gelatino-bromide  papers,  which  seem  particularly  liable  to 
blisters,  a  bath  of  chrome  alum  2  grs.,  water  i  oz.,  methylated 
spirit  i  oz.,  will  be  found  efficacious. 

Blue-Printing  Process.   See  Cyanotype. 

Blue  Tones  in  Prints.  A  sure  sign  of  over-toning,  due  to 
too  great  a  deposit  of  gold  (see  Toning),  or  to  sulphuration,  due 
to  an  acid  toning  bath. 

Blurring.  Any  image  possessing  an  indistinct  or  double 
outline  is  said  to  be  blurred,  and  may  be  caused  either  by 
movement  of  the  object  or  the  camera.  When  photographing 
in  a  high  wind,  a  loop  of  stout  twine,  tied  to  the  bottom  of  the 
tripod,  and  hanging  down  to  within  6  inches  of  the  ground,  in 
which  the  foot  can  be  placed,  will  be  found  to  steady  it.  (See 
also  Halation.) 

Borax  (Ger.,  Borax,  borsaiires  natron;  Fr.,  Borax;  Ital., 
Borace).  Na2B407,  ioH20=  179.  Synonyms:  Pyroborate,  Sodium 
borate,  or  Biborate.  It  occurs  in  colourless  octahedral  crystals 
containing  30  per  cent,  of  water,  or  in  hexagonal  prisms  with 
47  per  cent,  of  water  ;  also  as  an  amorphous  white  powder.  It 
is  found  native  in  various  parts  of  the  world,  or  made  by  neutral- 
ising boric  acid.  Solubility :  6  per  cent,  in  cold,  200  per  cent, 
in  hot  water;  very  little  soluble  in  alcohol,  60  per  cent,  in 
glycerine.  It  is  used  for  toning,  and  has  also  been  suggested  as 
an  addition  to  developers,  and  when  added  in  the  proportion  of 
3  parts  to  every  4  of  sulphate  of  iron  is  said  to  give  brilliancy  to 

44 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bro 


the  image.  It  is  a  restrainer  when  used  with  pyrogallol  andpyro- 
catechine,  but  an  accelerator  with  eikonogen  and  hydroquinone. 

Boric  Acid  (Ger.,  Borsdure ;  Fr.,  Acide  borique,  or  Boracique : 
Ital.,  Acido  boricd).  Synonym  :  Boracic  Acid.  H3B03  =  62, 
Occurs  native  in  several  parts  of  the  world.  Solubility,  4  per  cent, 
in  cold.  29  per  cent,  in  boiling  water,  25  per  cent,  in  alcohol. 
Of  very  limited  use  in  photography,  but  has  been  suggested  as 
an  antiseptic  in  conjunction  with  alum. 

Brenzcatechin.   See  Pyrocatechin. 

Brilliancy.  A  term  applied  to  negatives  to  denote  that  the 
lights  and  shadows  are  harmonious,  each  having  their  due  pro- 
portion of  deposit,  and  there  being  no  fog  ;  the  resulting  prints 
are  in  an  equal  way  perfect  in  their  power  of  rendering  light 
and  shade,  distance  and  effect.  This  can  only  be  obtained  by 
careful  attention  to  exposure  and  all  the  subsequent  manipu- 
lations. 

Broken  Negatives.  When  such  an  unfortunate  accident 
as  the  breakage  of  a  negative  occurs,  and  the  film  is  uninjured, 
it  may  be  removed  as  described  under  Stripping  Film  (q.v.) ; 
but  should  the  film  be  broken,  lay  the  negative,  film  downward, 
upon  a  perfectly  level  surface,  carefully  place  the  fractured 
pieces  together,  and  apply  strips  of  gummed  paper  along  the 
edges  of  the  negative.  When  thoroughly  dry,  turn  the  negative 
over,  and  apply  some  strips  of  paper  along  the  edge  on  the  film 
side  ;  allow  it  to  thoroughly  dry,  and  varnish  the  film.  To  print 
from  broken  negatives,  suspend  the  frames  from  an  ordinary 
roasting-jack,  or  place  the  frame  at  the  bottom  of  a  box  without 
a  lid  about  18  ins.  deep. 

Bromide  Paper.  Paper  coated  with  an  emulsion  of  bromide 
of  silver  in  gelatine  and  intended  for  obtaining  prints  by  develop- 
ment either  from  contact  printing  or  enlarging  by  daylight  or 
artificial  light. 

Emulsion  for  Bromide  Pafter  a?id  Opals.  Those  workers 
desirous  of  preparing  their  own  bromide  paper  and  opals  will  find 
the  following  directions  useful.  Dr.  Eder  states  that  "the 
emulsion  for  positive  prints  should  work  slowly,  have  little 
sensitiveness,  should  be  completely  free  from  fog,  and  give 

45 


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DICTIONARY  OF  PHOTOGRAPHY. 


delicate  details.  This  is  best  obtained  by  means  of  an  emulsion, 
which  contains  plenty  of  iodide  of  silver,  is  not  strongly 
ripened,  and  contains  plenty  of  gelatine."  He  suggests  the 
following : — 

No.  i.    For  Black  Tones. 

A.  Ammonium  bromide    20  parts. 

Gelatine    ...  50 — 80  „ 

Distilled  water    400  ,, 

Allow  the  gelatine  to  soak  in  the  water  for  twelve  hours,  then 
dissolve  at  a  temperature  of  50 — 6o°  C,  and  add  the  bromide ; 
then  in  the  dark  room  add  gradually,  with  constant  and  violent 
shaking,  the  following  solution  heated  to  50 — 6o°  C. : — 

Silver  nitrate    30  parts. 

Distilled  water   400  ,, 

Allow  the  solutions  to  stand  from  half  to  one  hour,  and  then  pour 
out  into  a  flat  dish  to  set.  When  thoroughly  set  break  up  into 
small  pieces,  and  wash  in  the  usual  manner. 

No.  2.    For  Brown  Tones. 

A.  Ammonium  bromide    18  parts. 

Potassium  iodide    2 — 4  ,, 

Gelatine    50 — 80  „ 

Distilled  water    400  M 

B.  Silver  nitrate    30  ,, 

Distilled  water    400  „ 

The  directions  for  making  the  same  as  above.  This  (No.  2) 
emulsion  gives  dark  brown  tones  with  ferrous  oxalate.  If  20 
parts  of  citric  acid  be  added  to  No.  2  A  the  tone  is  brighter.  If 
the  citric  acid  be  omitted,  and  4  parts  of  ammonia  be  added 
instead,  the  tone  is  a  darker  brown.  Commercial  bromide  paper 
is  usually  sold  in  three  grades — A,  smooth  surface  and  thin  paper 
suitable  for  mounting  and  small  prints ;  B,  smooth  surface  and 
thick  paper  suitable  for  larger  prints  and  book  illustrations  ;  and 
C,  rough  surface  and  thick  paper  suitable  for  enlargements. 
Some  manufacturers  also  issue  a  special  extra  rough  paper,  and 
others  a  paper  which  has  a  highly  glazed  surface  slightly  tinted 
and  obtained  by  coating  tinted  baryta  paper.     It  is  usually 

46 


DICTIONARY  OF  PHOTOGRAPHY.  [BrO 

stated  that  a  particular  class  of  negative  is  more  suitable  for 
bromide  paper,  but  almost  any  negative  may  be  used  provided  a 
suitable  paper  be  chosen  ;  for  very  dense  and  harsh  negatives  a 
rapid  paper  should  be  chosen,  for  thin  negatives  a  slow  paper  ; 
the  former  may  be  exposed  a  very  short  distance  from  the  light* 
the  latter  a  longer  distance.  For  all  bromide  contact-printing 
artificial  light  should  be  used,  either  gas  or  magnesium.  Com- 
mercial bromide  paper  is  sold  of  various  rapidities,  and  the 
following  table  is  calculated  from  one  by  Mr.  Alfred  Watkins. 


Eastman  permanent  slow  

...  50 

,,       hard  enamel 

...  50 

Nikko   

...  50 

,,       extra  rapid  (Eng.) 

10 

,,       extra  quick   

...  15 

. ,,       soft  enamel 

...  15 

Morgan  and  Kidd  

20 

Anthony  rapid   

6 

Eastman's  transferrotype  ... 

...  50 

Ilford  slow  ...   

...  100 

„     rapid   '  

10 

Dr.  Just's  ... 

...  75 

Mawson  and  Swan  

...  50 

In  this  table  the  sensitiveness  of  the  slowest,  is  placed  at  100, 
and  the  numbers  will  therefore  give  the  relative  exposures.  The 
important  item  for  successful  results  is  correct  exposure,  and  the 
simplest  method  of  ascertaining  this  is  one  by  Dr.  Herklots  Vos. 
The  standards  used  are  a  No.  5  Bray  burner  turned  up  to  its 
fullest  extent  without  flaring,  a  fixed  distance  for  exposure  from 
the  Bray  burner,  viz.,  two  feet,  a  fixed  scale  of  feet  from  the 
burner,  or  a  six-foot  inch  tape,  and  lastly  a  piece  of  flashed  opal, 
smoothed  or  ground  on  the  opal  side  (any  size  may  be  used,  but 
about  half-plate  will  be  found  convenient).  The  opal  glass  is 
placed  in  contact  with  the  film  of  the  negative,  and  the  two  held 
up  before  the  gas  burner,  the  negative  being  next  the  operator,  at 
the  full  length  of  six  feet  from  the  burner.  Now  examine  the 
image,  and  approach  the  negative  nearer  the  light  till  the  details, 
such  as  the  markings  on  a  brick  or  stone  wall,  or  the  trunk  or 
leaves  of  a  tree,  just  become  visible.   Note  the  distance  between 

47 


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DICTIONARY  OF  PHOTOGRAPHY. 


this  point  and  the  end  of  the  inch  tape,  and  give  an  exposure 
corresponding  in  number  of  seconds  to  number  of  inches — for 
instance,  the  details  of  negative  become  visible  36  inches  from 
the  six-foot  mark ;  therefore  36  seconds  exposure  will  be 
required  for  that  particular  negative  at  a  distance  of  two  feet 
from  the  burner.  An  alternative  method  is  to  cut  little  strips 
of  bromide  paper,  and  place  one  in  contact  with  the  half-tones, 
and  a  deep  shadow  of  the  negative,  and  give  the  strip  an  exposure; 
then  replace  by  another  strip,  and  give  a  longer  exposure ;  and 
then  repeat  for  a  third  time.  On  development  it  is  easy  to  see 
the  correct  exposure.  The  first  essential  for  development  is  of 
course  a  developer ;  and  for  enlargements  the  old  ferrous  oxalate 
still  stands  pre-eminent  as  the  best,  and,  we  think,  the  most  used, 
though  many  operators  now  use  quinol  or  eikonogen,  or  a 
mixture  of  the  two.  The  formula  for  a  good  all-round  ferrous 
oxalate  developer  is  given,  and  in  the  Appendix  will  be  found  the 
formulae  as  recommended  by  the  various  manufacturers  of  bromide 
paper. 

I. 

Neutral  oxalate  of  potash  ...    2,880  grs.  or  131  grms. 
Distilled  water    25  ozs.     500  c.  cm. 

II. 

Ferrous  sulphate     ...       ...  1,080  grs.    or    77  grms. 

Sulphuric  acid    2  drops  ,,     .3  c.cm. 

Distilled  water    7^  ozs.    ,,   500  ,, 

III. 

Bromide  of  ammonium      ...     480  grs.    or    1  grm. 
Distilled  water    30  ozs.    ,,   30  c.cm. 

To  make  the  developer,  add  one  part  of  solution  of  ferrous 
sulphate  to  six  parts  of  oxalate  solution,  and  a  few  drops  of 
solution  of  bromide  as  a  restrainer.  In  mixing  the  developer  it 
is  essential  that  the  solution  of  iron  be  added  to  the  oxalate,  and 
not  the  reverse,  or  a  thick  yellow  precipitate  of  ferrous  oxalate 
will  be  formed.  It  is  advisable  to  use  distilled  water  for  all 
solutions,  or  a  precipitate  of  oxalate  of  lime  will  be  formed,  and 
the  solution  will  be  clouded,  and  both  the  oxalate  and  ferrous 

48 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bro 


sulphate  solutions  should  be  distinctly  acid  to  test  paper. 
Another  formula  which  we  have  used  with  success  is  the 
following : — 

One  Solution  Formula. 


Neutral  oxalate  of  potash  ...       ...  2,600  grs. 

Citric  acid    100 

Ferrous  sulphate   975  M 

Boiling  distilled  water       ...       ...       ...      20  ozs. 


Dissolve  the  oxalate  in  the  water,  and  add  the  citric  acid,  and 
finally  the  ferrous  sulphate;  stir  till  the  whole  of  the  latter  is 
dissolved,  and  a  deep  orange  yellow  solution  is  formed.  For  use 
one  part  of  this  solution  is  diluted  with  three  parts  of  water,  or 
preferably  with  the  same  quantity  of  the  following  solution,  when 
it  will  be  about  equal  in  strength  to  that  made  by  the  first 
formula. 

Solution  for  Diluting  Concentrated  Developer. 

Neutral  oxalate  of  potash   120  grs. 

Distilled  water       ...    4  ozs. 

Another  formula  for  a  one-solution  developer,  which  was 
suggested  by  Carey  Lea,  the  well-known  American  scientist,  is 
as  follows  : — 

Neutral  oxalate  of  potash  1,600  grs. 

Distilled  water       ...  ...       ...      10  ozs. 

Heat  to  the  boiling  point,  and  add 

Ferrous  oxalate   500  grs. 

Stir  till  dissolved,  and  bottle  whilst  warm.  Some  ferrous 
oxalate  may  precipitate  out,  but  this  will  have  but  little  effect 
upon  the  action  of  the  developer,  which  is  a  saturated  solution 
of  ferrous  oxalate.  But  the  two  latter  methods  were  those  first 
used,  and  have  been  (gradually  supplanted  by  the  two-solution 
formula. 

Ferrous  Citro-Oxalate  Developer.  This  modification  of  the 
oxalate  developer  was  suggested  by  Abney  in  1881,  his  original 
formula  being : — 

49  E 


Bro] 


DICTIONARY  OF  PHOTOGRAPHY. 


Neutral  potassium  citrate   100  grs. 

Ferrous  oxalate    22 

Distilled  water       ...       ...       ...       ...       1  oz. 

The  citrate  of  potassium  is  dissolved  in  the  water  by  the  aid  of 
heat  and  the  ferrous  oxalate'  added,  and  the  whole  allowed  to 
cool.  A  more  convenient  method,  however,  which  Abney 
suggested  in  1882  is  to  make  two  solutions  as  follows : — 


Ferrous  sulphate   300  grs. 

Distilled  water       ...       ...       ...       ...     3^  ozs. 

The  solutions  are  mixed  in  equal  proportions  just  before  using. 
The  citro-oxalate  developer  does  not  require  any  addition  of 
bromide  as  restrainer,  its  action  not  being  quite  so  energetic  as 
the  ordinary  oxalate,  but  it  gives  a  fine  velvety  black  deposit  with 
most  papers.  Further  notes  on  modifications  and  additions  to 
the  oxalate  developer  will  be  found  in  the  Appendix. 

Pyrogallol  Developers.  Alkaline  pyrogallol,  having  a  great 
tendency  to  the  production  of  unpleasant  brown  tones,  and  also 
from  the  difficulty  of  preventing  stains,  has  never  yet  found 
much  use  for  enlarging  purposes,  and  therefore  no  formula  will 
be  given  for  this,  although  one  or  two  workers  have  advised 
the  same. 

Quinol  Developers.  Hydroquinone,  or  quinol,  has  been  used 
with  great  success  by  many  operators,  but  there  is  again  with 
this  developer  a  tendency  to  brown  in  the  deposit,  which  is 
extremely  unpleasing  to  some.  We  can  recommend  the  following 
or  black  tones : — 


Sulphurous  acid     r   20  minims. 

Distilled  water,  to  make    10  ozs. 


No.  1. 


Potassium  citrate 
Potassium  oxalate 
Distilled  water 


700  grs. 
200  „ 
3i  ozs. 


No.  2. 


154  grs. 
437  „ 


5° 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bro 


No.  2. 


Sodium  carbonate   ...  ...  ...  ...  1,300  grs. 

Potassium  hydrate  ...  ...  ...  ...  154 

Potassium  bromide ...  ...  ...  ...      20  ,, 

Distilled  water,  to  make  ...  ...  ...      10  ozs. 


Mix  in  equal  parts,  and  dilute  with  three  times  the  quantity  of 
water.  Other  formulae  recommended  by  manufacturers  will  be 
found  in  the  Appendix. 

Eikonoge?i.  We  have  found  the  following  formula  satisfac- 
tory : — 

No.  1. 

Eikonogen   50  grs. 

Sodium  sulphite      ...       ...       ...       ...  50 

Distilled  water,  to  make    ...       ...       ...      10  ozs. 

No.  2. 

Sodium  carbonate   ...    437  grs. 

Potassium  hydrate  ...       ...       ...       ...  56  ,, 

Distilled  water,  to  make    10  ozs. 

For  use  mix  in  equal  parts,  and  add  an  equal  quantity  of 
water. 

Eikonogen  and  Hydroquinonc.  The  most  satisfactory  formula 
we  have  yet  used  is  one  suggested  by  Mr.  J.  T.  Chapman,  of 
Manchester. 

No.  1. 

Quinol    40  grs. 

Eikonogen   120  ,, 

Sodium  sulphite     ...       ...       ...       ...    480  ,, 

Citric  acid    ...    20  ,, 

Distilled  water,  to  make    20  ozs. 

No.  2. 

Potassium  bromide  ...       ...       ...       ...       5  grs« 

Sodium  carbonate  pur.      ...       ...       ...  60,, 

Sodium  hydrate      ...    ...  3°  n 

Distilled  water,  to  make    20  ozs. 

Mix  in  equal  proportions,  and  add  an  equal  quantity  of 
water. 

51 


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DICTIONARY  OF  PHOTOGRAPHY. 


Clearing  and  Fixing.  The  paper  has  been  exposed,  and  our 
developer  made,  and  we  are  now  ready  for  the  all-important 
operation  of  development ;  but  before  giving  directions  for  this 
procedure  there  are  one  or  two  little  points  which  it  will  be  well 
to  explain.  It  is  advisable  to  have  four  or  five  dishes,  and  the 
most  convenient  are  the  deep  porcelain  kind.  Dishes  used  for 
ferrous  oxalate  development  must  be  used  for  no  other  purpose  ; 
dishes  which  have  been  used  for  pyro,  quinol,  eikonogen,  or 
fixing,  must  not  be  used,  or  stains  will  probably  occur.  The 
dishes  must  be  absolutely  clean,  and  so  must  the  measures  and 
hands.  Hypo  must  not  be  touched  till  the  whole  developing  has 
been  done  and  the  developer  and  developing  dish  put  away. 
Distilled  water  must  be  used for  all  operations  prior  to  clearing. 
After  these  important  points  have  been  observed,  the  operator 
may  reasonably  expect  good  results,  provided  the  exposure  and 
development  are  correctly  carried  out.  It  is  advisable  to  have 
four  or  five  dishes,  but  shift  may  be  made  with  a  less  number,  or 
home-made  dishes  may  be  constructed.  Keep  one  dish  solely 
for  the  developing,  and  mark  it  in  some  way  that  it  may  not  be 
used  for  any  other  purpose.  Mark  the  bottom  or  side  of  the  dish 
with  black  enamel  with  OX,  so  as  to  distinguish  it  easily. 
Arrange  three  or  four  dishes  side  by  side.  Into  the  first  pour 
distilled  water  till  about  one  inch  in  depth;  into  the  second, 
third  and  fourth  a  clearing  solution  is  poured  to  the  depth  of 
one  and  a  half  inches.  The  clearing  solution  is  made  as 
follows : — 

Acetic  acid   i  dr. 

Distilled  water       ...       ...       ...       ...     32  ozs. 

At  least  six  pints  of  this  solution  should  be  made.  The  hypo 
or  fixing  bath  should  not  be  touched  or  measured  out  till  the 
whole  of  the  developing  is  completed.  Now  take  an  exposed 
piece  of  paper  and  lay  it  face  downwards  on  the  distilled  water, 
and  as  soon  as  the  edges  begin  to  curl  up  lift  the  sheet  of  paper, 
turn  it  over  and  immerse  it  bodily  in  the  water,  and  allow  it  to 
soak  till  limp  ;  then  pour  the  distilled  water  off  into  a  jug  or  other 
convenient  vessel,  and  flood  the  paper  with  the  developer  in  one 
even  sweep;  rock  the  dish  till  the  image  begins  to  appear. 
Allow  the  development  to  continue  till  the  picture  appears  dense 
or  black  enough  in  the^  shadows,  when  by  this  time,  if  correctly 

52 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bro 


exposed,  the  half  tones  and  high  lights  will  be  full  of  detail.  At 
this  point,  then,  the  print  is  raised  from  the  developer  and 
immersed  at  once,  without  draining  or  washing,  into  the  first 
dish  containing  the  clearing  solution,  and  this  is  then  rocked  once 
or  twice,  and  allowed  to  remain  quiet.  The  developer  is  now 
poured  back  into  the  measure,  and  the  developing  dish  rinsed 
out  with  a  little  distilled  water,  and  drained,  again  filled  with 
distilled  water,  and  another  exposed  sheet  of  paper  treated  just 
like  the  one  as  described  above ;  but  while  the  paper  is  soaking 
in  the  developer,  the  already  developed  print  is  raised  from  the 
first  clearing  bath,  drained  slightly,  and  immersed  in  the  second 
clearing  bath.  Attention  is  now  turned  to  our  developing  print, 
and  when  this  is  developed  sufficiently  it  is  placed  in  the  first 
clearing  bath,  like  the  first  print,  without  draining  and  washing. 
We  now  proceed  to  treat  our  third  print  in  like  manner  to  the 
first  two  ;  and  as  soon  as  placed  in  the  developer  the  first  print 
is  removed  from  the  second  clearing  bath  and  placed  in  the  third, 
the  second  print  is  placed  in  the  second  bath,  and  this  leaves 
the  first  bath  ready  for  the  third  print.  When  three  prints  have 
been  cleared  in  the  first  bath,  it  is  poured  away,  and  the  second 
bath  put  in  its  place,  the  third  in  the  place  of  the  second,  the  first 
dish  now  being  in  the  third  place,  and  filled  with  fresh  clearing 
solution.  The  second  and  third  baths,  which  have  now  become 
the  first  and  second,  are  treated  in  a  similar  manner.  It  is  always 
as  well  to  use  a  good  quantity  of  developer,  as  it  can  be  used  for 
two  or  three  prints,  or  even  more,  without  any  loss  of  detail,  if 
the  developer  is  used  for  too  many  prints,  however,  the  latter 
gradually  become  lacking  in  detail  or  too  full  of  contrast.  The 
used  developer  need  not  be  thrown  away,  but  placed  on  one  side 
and  regenerated.  Having  finished  our  development,  the  develop- 
ing dish  is  washed,  dried,  and  put  away.  The  prints  still  in  the 
clearing  baths  are  placed  in  one  dish  and  flooded  twice  with 
fresh  clearing  solution,  the  solution  being  allowed  to  act  for  one 
minute  each  time,  and  then  well  washed  for  at  least  half  an 
hour  in  five  or  six  changes  of  water,  preferably  one  hour  in  ten 
changes  of  water.  The  print  is  then  ready  for  fixing,  which  may 
be  effected  by  immersing  for  ten  minutes  in 

Hyposulphite  of  soda    3  parts. 

Water    20  ,, 

53 


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DICTIONARY  OF  PHOTOGRAPHY. 


The  print  should  be  then  taken  out,  drained,  and  washed  at  once, 
or  preferably  placed  in  a  second  fixing  bath  of  the  same  strength 
as  the  above.  For  washing  the  prints  any  of  the  usual  washing 
tanks  may  be  utilised,  or  the  prints  may  be  placed  in  a  dish  and 
washed  by  changing  the  water  every  ten  minutes  for  at  least  two 
hours. 

Drying,  mounting,  and  finishing  the  prints.  To  dry  the 
washed  prints  it  is  advisable  to  hang  them  over  a  rod  or  cords. 
They  should  not  be  dried  between  blotting-paper.  We  have  suc- 
cessfully used  thin  laths  nailed  across  a  room,  on  which  the  prints 
are  laid.  Artificial  heat  should  not  be  used,  unless  it  is  warm 
air.  The  most  usual  method  of  mounting  enlargements  is  on 
cloth  or  canvas,  and  the  directions  given  by  the  Eastman  Company 
for  this  purpose  will  be  found  quite  satisfactory.  For  mounting 
upon  cards  it  is  best  to  allow  the  print  to  dry  thoroughly,  then 
place  it  face  downwards  upon  a  sheet  of  clean  paper,  and  apply 
freshly  made  starch  paste,  not  too  stiff,  with  a  brush,  and  rub 
into  contact  with  a  soft  cloth,  or  use  a  roller  squeegee.  Enlarge- 
ments should  always  be  mounted  behind  a  cut-out  mount,  and  a 
small  gold  edging  of  from  \  to  £  inch  or  more,  according  to  the 
size,  adds  to  the  appearance  ;  and  toned,  grey,  or  buff  mounts 
show  up  well.  The  smoother  varieties  of  bromide  paper  may  be 
both  rolled  and  burnished,  but  the  rough-surfaced  papers,  which 
are  the  more  artistic,  should  not  be  either  rolled  or  burnished. 
For  burnishing,  dry  Castile  soap  should  be  used,  or  else  an 
alcoholic  solution  of  soap  made  as  follows  ;  but  care  must  be 
exercised  in  the  use  of  the  latter,  or  stains  may  ensue: — 

Curd  soap    I  oz. 

Glycerine  soap    ^  oz. 

Shave  the  soap  finely,  rub  up  with  a  little  water,  and  heat 
till  dissolved,  adding  only  as  much  water  as  is  absolutely 
necessary  to  dissolve  the  soap.  This  solution  is  then  added 
gradually  to  32  ozs.  of  methylated  spirit,  well  shaken  and  filtered. 
A  pad  of  linen  or  cotton  wool  is  soaked  with  the  solution 
and  rubbed  over  the  dry  print,  which  is  ready  for  burnishing 
when  the  alcohol  has  evaporated.  Retouching  may  be  effected 
by  means  of  a  lead  pencil,  or  preferably  by  a  mixture  of  pow- 
dered graphite  and  crayon,  a  suitable  kind  of  the  latter  being 

54 


DICTIONARY  OF  PHOTOGRAPHY.  [BrO 

Conte-crayon  No.  i,  the  touches  being  afterwards  worked  up  with 
a  stump.  For  the  shadows  Conte-crayon  No.  3  should  be  used, 
whilst  for  the  high  lights  and  half  tones  a  harder  crayon,  such  as 
No.  o  or  No.  1,  will  be  found  useful.  Special  pencils  are  made 
for  retouching  bromide  prints  and  enlargements,  which  will  be 
found  to  answer  every  requirement.  Small  defects,  such  as  pro- 
duced by  pinholes  in  the  negative,  if  they  occur  in  a  high  light 
or  otherwise  white  place,  may  be  eradicated  by  scratching  out 
with  a  lancet  or  other  sharp-pointed  knife,  or  a  needle  mounted 
in  a  penholder.  Enlargements  on  rough-surface  paper  are 
specially  suitable  for  colouring  with  pastels  or  crayons,  water 
colours,  and  oil  colours,  by  means  of  the  air  brush,  etc.;  but  this 
department  would  need  more  space  than  can  well  be  devoted  to 
the  subject.  Colouring  with  pastels  or  crayons  is,  however, 
extremely  easy,  the  rough  surface  of  the  paper  taking  the  colour 
well.  For  water  colours  it  is  advisable  to  gently  rub  the  surface 
of  the  enlargement  with  a  pad  of  fine  linen  or  cotton  wool  dipped 
in  weak  ammonia  water,  so  as  to  make  the  colours  take  ;  or 
diluted  solution  of  ox-gall  may  be  used  for  the  same  purpose. 
The  enlargement  must  be  absolutely  dry  before  any  colour  is 
applied,  or  blisters  and  running  of  the  colours  will  ensue.  For 
finishing  in  oils,  the  enlargement  is  treated  as  follows.  We 
must  first  apologise  for  the  rough-and-ready  formula,  but  it 
was  obtained  from  a  professional  colourist,  who  had  used 
nothing  else  for  over  fifteen  years.  Obtain  one  pennyworth  of 
clear  size  and  dissolve  in  a  pint  of  warm  water,  and  flow 
over  the  enlargement  just  as  if  one  were  coating  a  dry  plate. 
The  film  must  not  be  touched  with  the  fingers.  When  quite 
evenly  covered,  set  the  canvas  up  about  four  feet  from  the 
fire  to  drain  and  dry,  when  it  will  be  found  that  the  oil  colours 
will  take  well,  and  yet  not  sink  in  and  stain  the  paper  or  canvas. 
Mr.  William  Brooks,  in  the  "Year  Book  of  Photography,"  1885, 
proposes  the  following  plan  for  the  greater  preservation  of  en- 
largements : — Good  white  shellac  is  dissolved  in  alcohol,  to  which 
solution  an  equal  quantity  of  a  saturated  solution  of  borax  in 
water  is  added  in  small  quantities,  and  shaken.  The  liquid 
should  be  quite  clear,  or  else  it  must  be  filtered,  and  it  should 
remain  clear  when  diluted  with  from  five  to  ten  times  the  quantity 
of  water.  The  enlargement  is  laid  flat  on  a  table  face  upwards, 
and  the  dilute  solution  is  sprayed  evenly  over  the  whole  surface 

55 


Bro] 


DICTIONARY  OF  PHOTOGRAPHY. 


by  means  of  a  spray  diffuser.  When  the  print  is  entirely  covered 
and  damp,  it  is  allowed  to  dry,  and  shows  no  trace  of  the  last 
treatment. 

Collodionising  and  Waxing  Bromide  Prints.  Bromide  prints 
may  be  given  a  slight  glaze  by  squeegeeing  the  print  whilst  wet 
down  to  waxed  plate  glass,  or  sheets  of  ebonite,  or  ferrotype  iron. 
A  still  higher  glaze  may  be  obtained  by  waxing  a  sheet  of  plate 
glass,  and  then  coating  it  with  enamel  collodion, 

Pyroxyline    ...       ...       ...       ...       ...       6  grs. 

Methylated  alcohol   i  oz. 

Ether   i 

As  soon  as  the  collodion  has  set  it  should  be  immersed  in  a  dish 
of  distilled  water  till  it  no  longer  shows  a  greasy  appearance,  and 
the  print,  previously  soaked  in  water  till  limp,  placed  in  contact 
with  the  collodionised  glass  under  water ;  and  both  should  be 
carefully  lifted  out,  the  print  well  squeegeed  down  till  no  air 
bubbles  are  visible,  and  then  the  whole  set  up  to  dry.  When 
thoroughly  dry,  the  edges  should  be  cut  round  with  a  sharp  knife 
and  the  print  stripped.  The  print  may  also  be  polished  with 
encaustic  paste,  which  improves  the  appearance  and  detail  in  the 
shadows  without  conferring  an  inartistic  gloss. 

Reducing  and  Intensifying  Bromide  Prints.  Sometimes  by 
an  error  of  judgment  a  bromide  print  or  enlargement  may  be 
over-developed  and  too  dark  and  heavy,  in  which  case  our  only 
remedy  is  to  resort  to  reduction  ;  and  most  of  the  methods 
adopted  for  landscape  work  may  here  be  applied.  The  most 
suitable,  however,  are  Howard  Farmer's  red  prussiate  of  potash 
reducer,  hypochlorite  of  soda,  or  Belitzski's  reducer. 

Howard  Farmer's  Reducer.  The  print  or  enlargement  is 
soaked  in  water  till  soft,  and  then  some  fresh  saturated  solution 
of  hyposulphite  of  soda  is  added,  and  the  dish  well  rocked ; 
then  a  few  drops  of  a  10  per  cent,  solution  of  potassium  ferri- 
cyanide  or  red  prussiate  of  potash  are  added  to  the  solution,  and 
this  again  applied  to  the  print.  Reduction  will  visibly  take 
place,  the  intensity  of  the  action  being  controlled  by  the  amount 
of  solution  of  red  prussiate  used.  The  print  should  be  removed 
before  the  exact  stage  of  reduction  is  reached,  as  this  action 
continues  slightly  during  the  process  of  washing. 

56 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bro 


Hypochlorite  of  Soda  Reducer.  For  this  reducer  two  solutions 
are  necessary,  one  the  so-called  Labarraque's  solution,  made  as 
follows  : — 

Chloride  of  lime    50  parts. 

Carbonate  of  soda   100  ,, 

Water   250  ,, 

Mix  the  chloride  of  lime  with  150  parts  of  water  and  the 
carbonate  of  soda  with  the  remainder ;  mix  the  two  solutions 
and  filter,  and  make  the  filtrate  measure  250  parts  by  washing 
the  filter  with  distilled  water.  The  second  solution  is  a  solution 
of  chrome  alum  made  by  dissolving 

Chrome  alum    10  parts. 

In  water   250  ,, 

To  make  the  actual  reducer,  15  parts  of  each  solution  are 
mixed  together  and  diluted  with  120  parts  of  water.  This 
mixture  is  first  thick  and  green,  but  gradually  becomes  clear 
yellow,  in  which  condition  it  should  be  flooded  over  the  print, 
previously  moistened  with  water.  The  action  of  the  reducer  is 
to  convert  the  image,  or  part  of  it,  into  chloride  of  silver,  which 
must  of  necessity  be  dissolved  by  ordinary  hypo.  Care  must  be 
exercised  that  reduction  is  not  carried  too  far. 

Belitzski's  Reducer.  This  is  the  method  which  in  our  hands 
has  given  the  best  results,  and  from  the  improved  formula  lately 
recommended  by  Herr  Belitzski  it  is  still  more  useful,  as  it  may 
be  kept  in  the  form  of  a  stock  solution.  The  formula  is  as 
follows : — 

Water   300  parts. 

Potassium  ferric-oxalate    ...       ...       ...      15  ,, 

Sodium  sulphite    15 

Dissolve,  and  add  to  the  blood-red  solution 

Oxalic  acid   5  parts, 

and  shake  till  the  solution  turns  green  ;  pour  off  from  any  un- 
dissolved oxalic  acid,  and  add 

Hyposulphite  of  soda        ...       ...       ...     75  parts. 

57 


Bro] 


DICTIONARY  OF  PHOTOGRAPHY. 


When  dissolved  it  is  ready  for  use.  To  reduce  the  print,  as 
soon  as  removed  from  the  fixing  bath,  rinse  with  water, 
flood  with  the  above  solution,  and  remove  as  soon  as  reduced 
sufficiently.  The  intensification  of  bromide  prints  is  by  no 
means  a  satisfactory  process ;  it  can  rarely  be  effected  without 
altering  the  colour  of  the  deposit.  There  are  one  or  two 
methods  applicable. 

Intensifying  with  Mercury  and  Re-development.  This  is 
perhaps  the  most  satisfactory  of  all  processes,  and  may  be 
effected  by  bleaching  the  print  in  a  solution  of  mercuric  chloride, 
and  then  re-developing  with  an  old,  used  ferrous-oxalate  de- 
veloper. 

Intensifying  with  Monckhoveris  Silver  Cyanide.  The  obj ection 
to  the  use  of  this  formula  is  that  one  cannot  make  sure  of 
obtaining  a  black  tone  in  the  intensified  print,  the  colour  of  the 
image  tending  towards  a  brown. 

Intensifying  with  Silver.  It  may  be  quite  possible  to  intensify 
bromide  prints  with  an  acid  silver  and  iron,  or  acid  silver  and 
pyrogallol  intensifier ;  but  we,  so  far,  have  been  unable  to  obtain 
results  free  from  stains. 

Intensifying  with  Uranium.  The  application  of  Selle's  pro- 
cess of  uranium  intensification,  first  suggested  for  collodion 
negatives  in  1865,  has  been  suggested  as  a  toning  process  for 
bromide  paper,  but  it  is  purely  an  intensification  process.  The 
following  formula,  which  is  a  modification  of  the  original  one, 
acts  well : — 

Potassium  ferridcyanide    1  part. 

Uranyl  nitrate    1 

Acetic  acid   20  parts. 

Distilled  water       ...       ...       ...       ...    200  ,, 

The  print,  when  perfectly  free  from  hypo,  should  be  soaked 
in  water  till  limp,  and  then  the  above  solution  applied.  When 
the  intensification  has  proceeded  far  enough,  wash  thoroughly 
for  half  an  hour  in  water  acidulated  with  acetic  acid. 

Conversion  of  the  Image  into  Platinum.  The  silver  image  ol 
the  bromide  print  may  be  converted  into  platinum  by  the 
following  process,  first  suggested  by  Vidal  in  1887.  The  well- 
washed  print  is  immersed  in  the  following  bath : — 

58 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bro 


Platinum  perchloride    I  part. 

Distilled  water    ...  2000  parts. 

Hydrochloric  acid   25  „ 

till  the  desired  tone  is  obtained.  E.  Vogel,  junior,  recommends 
the  following — 

Chloroplatinite  of  potash   1  part. 

Distilled  water       ...       ...       ...       ...  1000  parts. 

Hydrochloric  acid   ...      10  „ 

The  print  is  placed  in  this  for  about  twenty  minutes,  and  is  then 
thoroughly  washed  and  fixed.  To  prove  the  substitution  ot 
platinum  for  silver,  place  the  print  in  a  solution  of  cupric  chloride 
made  as  follows  : — 

No.  1. 

Calcium  chloride,  crystal   ...      10  parts. 

Distilled  water    50  M 

No.  2. 

Sulphate  of  copper,  crystal  ...       ...      15  parts. 

Distilled  water       ...       ...       ...       ...    100  ,, 

When  the  salts  are  dissolved,  mix  the  two  solutions  and  pour  on 
to  a  filter  paper,  and  allow  the  filtrate  to  drain  through,  and 
wash  the  filter  paper  with  50  parts  of  distilled  water.  The 
print,  or  a  portion  of  it,  is  soaked  in  the  filtrate,  when  any  silver 
remaining  in  the  image  will  be  converted  into  chloride,  and  may, 
after  washing,  be  removed  by  the  use  of  the  ordinary  fixing 
bath  ;  or  if  the  image  appear  pale  and  wanting  in  intensity,  it 
may  be  redeposited  in  the  shape  of  metallic  silver  by  applying 
an.  old  ferrous  oxalate  developer.  If  the  print,  after  being  treated 
with  the  cupric  chloride  solution,  be  exposed  to  actinic  light,  the 
image  can  be  developed  in  shades  varying  in  colour  according 
to  the  duration  of  the  second  exposure. 

Failures. 

The  exposure  has  been  over-estimated ;  in  other  words,  the 
enlargement  is  over-ex fiosed.  This  is  at  once  recognised  by  the 
resulting  print  being  flat,  wanting  in  contrast,  or  sunken  in.  The 
whites  even  may  not  be  pure,  but  show  signs  of  reduced  silver  ; 

59 


BrO]  DICTIONARY  OF  PHOTOGRAPHY. 

the  image  is  also  a  dull  grey,  and  contains  no  rich  blacks.  The 
obvious  remedy  is  to  shorten  the  exposure,  but  the  over-exposed 
print  may  also  be  improved  by  a  process  of  intensification. 

The  exposure  has  been  under-estimated,  or  the  enlargement  is 
under-exposed.  An  under-exposed  bromide  print  is  full  of  ex- 
treme contrast,  the  shadows  black  and  heavy,  and  the  high  lights 
wanting  in  detail,  and  showing  bare  patches  of  paper.  Increas- 
ing the  exposure  is  the  only  remedy,  and  an  under-exposed  print 
had  better  be  consigned  to  the  residue  box  rather  than  shown. 

The  print  is  fiat,  and  wanting  in  contrasts,  and  does  not  even 
show  white  paper  under  the  pins  or  bands  which  hold  it  on  the 
easel.  This  is  probably  due  to  stray  actinic  light.  The  room  in 
which  the  enlargement  is  made,  and  the  lantern,  if  such  be  used, 
should  be  examined  for  stray  leakage.  Such  a  print  may  be 
improved  by  slightly  reducing,  washing,  thoroughly  converting 
the  image  into  chloride  of  silver,  and  redeveloping. 

Faults  due  to  the  Developer. 

The  print  during  development  becomes  covered  with  a  sandy 
yellow  deposit.  This  may  be  caused,  first,  by  too  much  acid  in 
the  developer ;  second,  by  want  of  acid  in  the  developer ;  third, 
by  using  too  much  ferrous  sulphate ;  fourth,  by  using  too  little 
oxalate  solution.  The  remedy  for  the  second  cause  is  the  addi- 
tion of  some  acid  to  the  developer,  both  to  the  oxalate  and  iron 
solutions.  Ferrous  oxalate,  formed  by  the  addition  of  ferrous 
sulphate  solution,  is  soluble  only  in  excess  of  oxalate  of  potash  ; 
therefore,  if  too  much  iron  solution  be  added,  some  of  the  ferrous 
oxalate  will  be  precipitated.  In  such  a  case  pour  off  the  de- 
veloper, and  add  more  oxalate  solution  and  a  grain  or  two  of 
oxalic  acid.  If  the  oxalate  solution  is  allowed  to  sink  to  too 
low  a  temperature  some  of  the  oxalate  will  crystallise  out,  and 
the  solution  thus  be  weakened.    The  remedy  is  obvious. 

The  print  during  development  becomes  covered  with  a  white 
chalky  deposit.  This  deposit,  which  is  oxalate  of  lime,  is  caused 
by  using  ordinary  tap  or  hard  water  for  soaking  the  print  or  for 
diluting  the  developer.  The  remedy  is  obviously  the  use  of  dis- 
tilled water.  When,  however,  such  a  deposit  occurs,  the  only 
plan  is  to  continue  the  development  till  the  print  is  done  enough, 
a»d  then  remove  the  deposit  by  a  weak  hydrochloric  acid  or 
sulphuric  acid  bath. 

60 


DICTIONARY  OF  PHOTOGRAPHY.  [BrO 

The  print  is  under-developed.  This  is  known  by  the  print 
being  full  of  gradation  and  detail,  but  not  sufficiently  dense  or 
black  enough  in  the  shadows.  The  addition  of  a  little  more 
ferrous  sulphate  solution  and  longer  development  is,  of  course, 
the  remedy.  In  the  case  of  a  finished  print  intensification  is  the 
only  remedy. 

The  print  is  over-developed.  This  is  known  by  the  print  being 
too  dark  and  heavy.  The  use  of  less  iron  or  shortened  duration 
of  development,  or,  in  the  case  of  a  finished  print,  reducing  the 
same. 

Faults  due  to  the  After-Operatiotis  of  Clearing,  Fixing, 
Washing,  etc. 

The  print  is  yellow.  This  must  not  be  confounded  with  the 
yellow  deposit  of  ferrous  oxalate,  this  yellowness  being  caused, 
first,  by  washing  the  print  between  development  and  clearing,  or 
leaving  it  too  long  a  time  before  immersing  in  the  clearing  bath  ; 
second,  insufficient  acid,  or  too  little  clearing  bath ;  third,  in- 
sufficient washing  between  clearing  and  fixing  ;  fourth,  insufficient 
washing  after  fixing,  (i)  The  cause  of  this  yellow  stain  is  the 
action  of  the  air  upon  the  iron  salt,  or  by  the  action  of  the  alkaline 
and  earthy  salts  in  common  water,  when  the  print  is  washed 
between  development  and  clearing.  The  sole  action  of  the 
clearing  solution  is  to  eliminate  the  soluble  iron  salt,  and  prevent 
the  precipitation  of  any  insoluble  iron  compound.  (2)  Insufficient 
acid  or  insufficient  use  of  the  clearing-bath  tends  to  exactly  the 
same  results  as  given  under  No.  1.  (3)  Insufficient  washing 
between  clearing  and  fixing  produces  not  exactly  the  same  kind 
of  yellow  stain.  With  the  two  former  cases  the  stain  is  generally 
more  or  less  defined,  and  tends  to  an  orange  hue,  whilst  the 
third  fault  in  manipulation  is  generally  characterised  by  a  faint 
general  yellow  or  lemon  tint  all  over  the  print ;  and  it  arises,  in 
this  case,  from  the  decomposition  of  the  hypo  by  the  acid  of  the 
clearing-bath,  and  consequent  deposition  of  sulphur  in  the  film 
and  paper.  (4)  Insufficient  elimination  of  hypo  or  imperfect 
fixation  tends  to  subsequent  yellowing  of  the  paper  consequent 
on  the  decomposition  of  the  hyposulphites  of  silver.  Using  a 
fixing-bath  too  long  or  too  weak  also  gives  rise  to  the  same 
result,  or  not  allowing  the  prints  to  stay  sufficiently  long  in  the 
hypo  will  also  cause  the  same  effect.     The  prevention  of  these 

6r 


Bro] 


DICTIONARY  OF  PHOTOGRAPHY. 


faults  is  obvious.  The  cure  of  the  same,  when  existent,  depends 
solely  upon  the  nature  of  the  fault.  Thus,  if  the  yellow  colora- 
tion be  due  to  a  compound  of  iron,  it  may  frequently  be  removed 
by  using  a  bath  of 

Sulphuric  acid    25  parts. 

Water    500  ,, 

or 

Neutral  oxalate  of  potash   25  parts. 

Oxalic  acid  ...       ...       ...       ...       ...  5 

Sulphuric  acid    5 

Distilled  water    500  ,, 

The  prints  should  be  allowed  to  soak  in  either  of  these  baths  for 
about  ten  minutes,  and  then  thoroughly  washed.  If  the  stain  is 
still  persistent,  it  may  be  assumed  to  be  sulphur  deposited  in  the 
paper.  We  have  found,  however,  that  many  a  yellow  stain  on 
bromide  paper  will  yield  to  the  following  treatment,  although  it 
may  refuse  to  budge  by  treatment  with  either  of  the  above  baths. 
The  print  is  thoroughly  well  wetted  and  laid  at  the  bottom  of  a 
dish,  with  just  sufficient  water  to  make  it  adhere  flat  to  the  bottom 
without  floating  about.  The  following  powder  is  then  sifted 
over  the  print ;  it  may  also  be  applied  in  the  form  of  a  paste. 
When  sifted  over  the  wet  print  it  should  form  a  damp,  sticky 
mass ;  and  this  may  be  allowed  to  remain  on  the  print  for  half 
an  hour,  and  then  well  washed  and  dried. 

Salt  of  sorrel    15  parts. 

Cream  of  tartar    5  ,, 

The  salt  of  sorrel  is  the  so-called  quadroxalate  of  potash  or  acid 
oxalate. 

Blisters.  These  pests  sometimes  make  their  appearance  when 
using  bromide  paper,  usually  in  the  first  washing  water  after  fix- 
ing, and  they  may  be  partially  prevented  by  adding  a  handful  of 
salt  to  the  first  washing  water  after  fixing,  or  preferably  by  using 
the  following  bath  just  after  clearing  : — 

Chrome  alum         ...       ...       ...       ...  25  parts. 

Sulphuric  acid    6  ,, 

Water    250  „ 

62 


DICTIONARY  OF  PHOTOGRAPHY. 


[Bro 


It  is,  of  course,  absolutely  necessary  that  the  print  should  be 
well  washed  to  eliminate  the  alum,  or  yellow  stains  would  ensue 
from  the  decomposition  of  the  hypo  by  the  alum,  and  consequent 
deposition  of  sulphur. 

It  seems  almost  unnecessary  to  give  any  preambulatory  notes 
as  to  the  cause  for  the  desire  for  warm  tones  on  bromide  paper. 
The  Eastman  Company  first  suggested,  we  believe,  the  applica- 
tion of  uranium  to  the  finished  print  on  their  transferrotype  paper, 
to  give  a  warmth  and  colour  which  could  not  be  obtained  by 
ordinary  development,  but  they  pointed  out  that  it  was  essentially 
a  process  of  intensification  ;  and  one  cannot  help  feeling  very 
strongly  that  it  is  so,  and  that  it  has  a  tendency  to  strengthen  up 
the  distance  so  as  to  destroy  to  some  extent  the  atmospheric 
effect.  In  Anthony's  International  Annual,  1889,  p.  266,  I  stated 
that  experiments  had  been  commenced,  which  would  enable  any 
one  to  obtain  warm  tones  even  to  purple  shades  on  bromide 
tints;  and  in  the  succeeding  volume,  1890,  p.  340,  I  suggested 
bleaching  the  image  with  a  chlorising  agent,  and  then  reducing 
with  sulphantimonite  of  soda  or  a  weak  developer.  Senier 
recommended  the  chlorising  of  the  image  and  redevelopment* 
and  A.  R.  Dresser  suggested  bleaching  with  mercury  and  re- 
development with  quinol.  In  his  excellent  book,  "  Leitfaden 
fiir  den  Positiv-Entwicklungs-process  auf  Gelatine-Emulsions 
Papier,"  etc.,  Dr.  E.  A.  Just  suggests  the  use  of  the  alkaline 
developers  for  obtaining  warm  tones ;  and  Dr.  Stolze  ("  Photo- 
Nachrichten,"  1891,  p.  4)  gives  a  summary  of  his  experiments 
to  obtain  warm  tones  by  various  developers,  and  finally  suggests 
giving  a  long  exposure,  and  developing  with  the  following : — 

A. 

Sodium  sulphite    20  parts. 

Eikonogen   4  ,, 

Water    300  „ 


B. 


Potash  carbonate 
Water 


50  parts. 
300 


To  obtain  brownish  tones,  the  actual  developer  must  be  com- 
pounded as  follows : — 

63 


Bro]  DICTIONARY  OF  PHOTOGRAPHY. 

Solution  A   50  parts. 

»      B    ...    20  „ 

Water    150-180  „ 

To  every  100  parts  of  this  add 

Solution  of  bromide  of  potash  (1  :  10)    ...  5-10  parts. 

Brown  or  blackish  brown  tones  only  are  to  be  thus  obtained. 
Dr.  Stolze  also  suggests  bleaching  the  image  with  a  solution  of 
bromide  of  copper,  stating  that  this  is  preferable  to  chlorising 
the  image,  as  stains  are  less  likely  to  appear.  The  bromide  of 
copper  solution  can  be  made  by  dissolving : — 

A. 

Copper  sulphate    1  part 

in 

Distilled  water    100  parts  ; 

B. 

Potassium  bromide   1  part 

in 

Distilled  water       ...       ...       ...       ...    100  parts, 

and  mixing  the  two  solutions  ;  the  thus  bromised  image  should 
be  well  washed,  and  then  exposed  to  daylight  and  redeveloped 
with  the  above  eikonogen  developer  mixed  in  the  following 
proportions : — 

Solution  A   50  parts, 

„      B   20  „ 

Water   5000  „ 

Bromide  Pencils.  Special  pencils  for  retouching,  spotting 
out  and  working  up  bromide  prints  and  enlargements. 

Bromides.  These  are  salts  formed  by  the  union  of  bromine 
with  a  base.  The  alkaline  bromides,  potassium  and  ammonium, 
are  used  as  restrainers,  or  for  emulsion  making.  The  question 
often  arises  as  to  whether  these  two  are  of  equal  efficiency  as 
restrainers,  but  has  not  been  satisfactorily  answered.  If  Abney's 
view  of  their  action  be  accepted,  then  the  ammonium  salt  should 
be  the  stronger.    He  says  :  "  In  the  formulae  with  pyrogallic  acid, 

64 


DICTIONARY  OF  PHOTOGRAPHY. 


[Cad 


it  will  be  noticed  that  a  soluble  bromide  is  recommended  to  be 
added  to  the  solution  of  pyrogallic  acid  and  ammonia.  This  is  to 
check  the  reduction  of  the  unaltered  silver  bromide,  the  soluble 
bromide  seemingly  forming  a  compound  with  it,  which  is  much 
less  attackable  by  the  developer." 

Bromine  (Ger.,  Brom;  Fr.,  Brome;  Ital.,  Bromo).  Br  =  80. 
A  non-metallic  element  obtained  as  a  deep  orange-red  liquid 
from  seaweed.    It  is  used  to  form  the  bromides. 

Bronzing.  A  peculiar  metallic  lustre  seen  on  looking  at  the 
shadows  of  some  prints  at  a  certain  angle.  It  only  makes  its 
appearance  on  paper  sensitised  on  a  very  strong  bath,  and  with 
negatives  showing  very  bold  contrast.  It  usually  disappears  in 
the  fixing  bath.  If  this  should  still  show  after  fixing  and  drying, 
the  use  of  a  little  Encaustic  Paste  {q.v.)  will  remove  the  same. 

Buckle  Brush.  A  convenient  little  instrument,  made  by 
drawing  a  piece  of  silver  wire  bent  in  half  through  a  piece  of 
small  glass  tubing,  a  tuft  of  cotton-wool  being  caught  in  the  arch 
of  the  wire ;  the  great  advantage  of  this  little  dodge  being  that, 
when  dirty,  the  cotton-wool  can  easily  be  replaced. 

Burnishing  is  the  operation  of  drawing  prints  over  the  surface 
of  a  heated  roller,  the  print  being  brushed  over  with  a  lubricator 
made  by  dissolving  five  grains  of  Castile  soap  in  an  ounce  of 
methylated  spirit.  This  should  be  rubbed  over  the  face  of  the 
print  with  a  piece  of  flannel,  and  allowed  to  dry  before  burnish- 
ing. The  hot  bar  of  burnisher  should  be  just  hot  enough  to  be 
comfortably  held  in  the  hand.  No  stoppage  must  occur  in  the 
movement  of  the  print  whilst  on  the  burnisher,  or  a  line  will  be 
caused  across  the  finished  print.  Should  the  bar  of  the  burnisher 
become  scratched  at  any  time,  it  should  be  repolished  with  the 
finest  emery  ground  into  a  paste  with  oil. 

Cabinet.  A  special  size  of  the  commercial  photograph,  which 
measures  about  6  by  4  ins. 

Cadmium  and  Ammonium  Bromide  (Ger.,  Ein/ack-am- 
monium-cadminmbromid ;  Fr.,  Bromure  double  de  cadmium 
et  d' ammonium  ;  Ital.,  Broinuro  doppio  di  cadmio  c  d'ammonio). 
2CdBr22NH4BrH20  =  758.  This  salt  is  formed  by  dissolving  344 
parts  of  cadmium  bromide  and  98  parts  of  ammonium  bromide 

65  F 


Cad] 


DICTIONARY  OF  PHOTOGRAPHY. 


in  water,  evaporating  and  crystallising :  130  parts  are  soluble  in 
100  parts  of  cold  water,  and  1  part  in  53  parts  of  absolute  alcohol, 
and  1  part  in  24  parts  of  alcohol  and  ether  (1  :  1).  This  salt  is 
preferred  to  the  simple  bromide  for  collodion  work  on  account  of 
its  greater  solubility. 

Cadmium  and  Ammonium  Iodide  (Ger.,  Zweifach  am- 
monium-cadmiumiodid  ;  Fr„  lodure  double  \  de  cadmium  et 
d' ammonium;  Ital.,  Ioduro  doftpio  di  cadmio  et  d'ammonio) 
CdL,  2NH4I,  2H20  =  565.  This  salt  is  formed  in  a  similar 
manner  to  the  double  bromide  by  dissolving  183  parts  of  cadmium 
iodide  and  145  parts  of  ammonium  iodide,  evaporating  and 
crystallising.  One  part  is  soluble  in  07  parts  of  absolute  alcohol 
and  in  r8  parts  of  alcohol  and  ether  (1  : 1).  It  is  used  in  the 
collodion  process,  and  is  preferred  to  the  single  salt  on  account 
of  its  greater  stability  and  greater  solubility. 

Cadmium  Bromide  (Ger.,  Cadmiumbromid,  or  Bromcad- 
mium;  Fr.,  Bromure  de  cadmium;  Ital.,  Bromuro  di  cadmio). 
CdBr24H20  =  344.  One  part  by  weight  is  soluble  in  0-94  part  of 
cold  and  1  part  of  hot  water,  in  3*4  parts  of  absolute  alcohol, 
in  250  parts  of  ether,  and  16  parts  of  alcohol  and  ether  (1  :  1).  It 
crystallises  in  small  efflorescent  needles,  and  is  formed  by  direct 
combination  between  bromine  and  cadmium,  or  cadmium  and 
hydrobromic  acid.  At  ioo°  C.  the  crystals  lose  two  molecules  of 
water  and  all  the  water  at  2000  C.  It  is  used  in  the  manufacture 
of  bromised  collodion. 

Cadmium  Iodide  (Ger.,  Cadmiumiodid,  or  Iodcadmium ;  Fr„ 
lodure  de  cadmium ;  Ital.,  Ioduro  di  cadmio).  Cdl2  —  466. 
This  salt  is  formed  in  a  similar  manner  to  the  bromide,  and  it 
is  the  most  stable  of  all  iodide  salts.  One  part  dissolves  in  1*13 
parts  of  water,  in  0-98  parts  of  absolute  alcohol,  in  3-6  parts  ot 
ether,  and  in  2  parts  of  alcohol  and  ether.  It  is  used  in  the 
collodion  process. 

Calcium  Carbonate  (Ger.,  Calciumcarbonat,  Kohlensaures 
Kalk,  Kreide;  Fr„  Carbonate  de  chaux ;  Ital.,  Carbonate  di 
calce).  CaC03  =  100.  This  occurs  native  in  various  forms, 
such  as  Iceland  spar,  marble,  chalk,  etc.  It  is  almost  insoluble 
in  water,  0*007  per  cent,  being  taken  up  by  cold  and  0*005  Per 
cent,  by  hot  water ;  insoluble  in  alcohol  and  ether ;  it  is  soluble 

66 


DICTIONARY  OF  PHOTOGRAPHY. 


[Cal 


in  water  containing  carbonic  acid,  a  soluble  salt,  Ca(HC  O ) 
being  formed.    It  is  used  for  cleaning  glass,  in  toning-baths,  and 
tor  preparing  other  calcium  salts. 

Calcium,  Chloride  of  (Ger.,  Calciumchlorid ';  Fr.,  Chlorure 
de  calchcm;,  Ital.,  Cloruro  di  calcio).  CaCL=iii.  Made  by 
dissolving  chalk  in  hydrochloric  acid,  and  evaporating  the  solu- 
tion. One  part  is  soluble  in  -25  parts  of  cold  water  and  -15  of 
hot,  in  7  parts  ot  absolute  alcohol.  The  salt  is  met  with  in  two 
forms — as  a  crystalline  substance  and  also  in  the  form  of  white 
agglutinated  masses.  The  latter  form  is  used  for  the  preservation 
of  platinotype  paper,  and  acts  by  absorption  of  the  aqueous 
vapour  from  the  air;  and  it  will  be  found  in  time  to  become 
very  moist,  and,  if  left  long  enough,  quite  liquid.  In  either  case 
it  should  be  collected  in  a  common  jar  or  vessel,  and  placed 
in  a  hot  oven,  when  the  water  absorbed  will  be  driven  off, 
and  the  salt  will  be  as  good  as  new  so  far  as  its  hygroscopic 
qualities  go. 

Calcium  Hydrate  (Ger.,  CalciumJiyJroxid ;  Fr.,  Hydrate 
de  chaux ;  Ital.,  Cake  spentd),  Ca(OH)a  =  74.  Synonyms  : 
Calcium  Hydroxide,  Hydrate  of  Lime,  Slaked  Lime.  Prepared 
by  moistening  quick  lime  with  water.  It  is  a  white  powder,  and 
is  soluble  in  760  parts  of  cold  water,  less  soluble  in  hot  water ; 
its  solution  is  called  lime-water. 

Calcium  Oxide.    See  Lime,  Quick. 

Calcium  Tube.  This  is  usually  a  metal  tube  with,  at  one 
end,  a  separate  chamber  to  contain  Calcium  Chloride  {q.v.),  and 
is  used  to  prevent  the  action  of  moisture  on  certain  papers,  such 
as  platinotype,  etc. 

Calorific  Rays  of  the  Spectrum.  Those  rays  of  the  spectrum 
which  produce  or  emit  heat.  They  are  found  at  the  red  end 
of  the  spectrum,  the  most  powerful  being  situated  beyond  the 
visual  rays.  This  can  be  proved  in  the  following  manner: — 
The  rays  of  the  spectrum  are  conducted  through  a  solution 
of  iodine,  which  absorbs  all  visual  rays,  but  allows  the  heat 
rays  to  pass ;  these  can  be  brought  to  a  focus  by  certain 
means,  and  in  this  focus  magnesium  ribbon  will  catch  fire,  and 
platinum  be  brought   to  a  white  heat.     Taking   100  as  the 

67 


Cal] 


DICTIONARY  OF  PHOTOGRAPHY. 


maximum  intensity  of  the  heat  rays,  the  following  table  will 
give  the  values  of  the  colours  of  the  spectrum  as  heat- 
producers  : — 

Violet    o 

Green    2 

Yellow    14 

Red   21 

End  of  visual  spectrum   45 

Ultra  red,  or  invisible  rays          ...       ...  100 

Bodies  which  have  the  power  of  transmitting  heat  rays  are  said 
to  be  diathermanous,  those  which  do  not  possess  this  power, 
athermanbus.  Glass  being  comparatively  poor  in  diathermanous 
power,  photographic  lenses,  unless  pointed  at  the  sun,  allow  but 
few  heat  rays  to  pass  to  the  sensitive  film. 

Calotype,  or  Talbotype.  A  process  named  after  its  inventor, 
Fox  Talbot,  but  little  used  now,  but  interesting  from  its  being 
the  first  paper  negative  process  used.  The  following  is  a  short 
resume  of  the  process  : — Stout  paper,  of  an  even  surface  and  as 
grainless  as  possible,  is  brushed  over  with  a  solution  of  iodide 
of  silver  in  iodide  ot  potassium.  It  is,  when  partially  dry,  washed 
twice  or  three  times  in  distilled  water  to  remove  the  iodide  of 
potassium  and  dried,  and  it  can  be  kept  for  some  little  time  in 
this  state,  as  it  is  but  faintly  sensitive  to  light.  When  required 
for  exposure  it  is  brushed  over  with  a  solution  of  gallo-nitrate  of 
silver  or  aceto-gallo-nitrate,  and  exposed  wet;  the  exposure 
required  for  an  open  view  is  about  six  minutes.  In  all  cases 
a  faint  image  of  sky-line  should  be  apparent.  The  image  is 
developed  with  a  solution  of  gallo-nitrate  of  silver  in  excess  of 
gallic  acid.  The  negative  is  then  well  washed,  fixed  in  hypo, 
and  washed  and  dried  in  the  usual  way,  then  waxed  or  oiled  to 
render  it  translucent. 

Cameo.  Photographs  to  which,  by  means  of  dies  and  press,  a 
slight  convexity  is  given  of  differing  shapes. 

Camera  Obscura  is  actually  a  dark  chamber  into  which  the 
image  of  external  objects  may  be  projected  by  means  of  a  con- 
vex lens,  and  a  mirror  placed  behind  it  at  an  angle  of  450. 
Portable  camera  obscuras  were  made,  by  means  of  which  the 

68 


DICTIONARY  OF  PHOTOGRAPHY. 


[Car 


images  ol  exterrial  objects  were  projected  upon  a  sheet  of  white 
paper,  and  the  outlines  traced  by  means  of  a  pencil.  From  this 
was  conceived  the  idea  of  the  present  camera,  with  certain 
modifications  to  allow  the  action  of  light  to  portray  more 
faithfully  and  easily  what  the  hand  had  done. 

Camera  Stand.   See  Stand. 

Camphor  (Ger.,  Camphor ;  Fr.,  Camphrc ;  Ital.,  Canford). 
This  is  obtained  from  several  trees  from  Japan  and  Borneo.  It 
is  met  with  in  solid,  colourless,  translucent,  crystalline  masses, 
usually  covered  with  minute  fissures  ;  it  is  very  tough,  but  can  be 
powdered  by  moistening  with  water,  alcohol,  or  ether.  It  has  a 
peculiar  smell  and  hot,  bitter  taste.  It  is  soluble  01  per  cent, 
in  water,  120  per  cent.'in  alcohol,  and  also  in  ether  and  most 
oils.  It  is  used  in  the  preparation  of  celluloid,  varnishes,  and 
as  an  antiseptic. 

Canada  Balsam  (Ger.,  Canadabalsam  ;  Fr.,  Baume  du  Canada; 
Ital.,  Balsamo  del  Canada).  Synonym  :  Canada  Turpentine.  A 
pale  greenish  and  faintly  yellow  turpentine  obtained  from  various 
species  of  pine  trees.  It  has  the  consistence  of  honey,  and 
a  pleasant  resinous  odour.  It  slowly  dries  by  exposure  to.  the 
air  into  a  transparent  adhesive  varnish.  Insoluble  in  water, 
soluble  in  all  proportions  in  alcohol.  It  is  used  for  making 
varnishes,  and  for  cementing  lenses  together. 

Canvas,  Printing  on.   See  Silk. 

Cap.  The  cover  used  at  the  time  of  exposure  to  open  and 
close  the  lens.  It  is  also  a  protection  against  accidental  injury. 
The  author  has  a  cap  made  for  both  ends  of  the  lens  for  greater 
protection  of  the  glasses.  To  prevent  accidental  losing  or  mis- 
laying of  the  cap,  it  should  be  attached  to  the  lens  mount  by  a 
piece  of  string. 

Carbolic  Acid  (Ger.,  Carbolsaure ;  Fr.  Acide  Phenique). 
C6H5HO=Q4.  Synonyms:  Phenic  Acid,  Phenol,  Phenylic 
Alcohol,  Hydrate  of  Phenyl.  A  crystalline  substance,  which  is 
not  a  true  acid,  obtained  from  coal  tar  by  fractional  distillation. 
It  is  a  powerful  antiseptic  and  preservative,  for  which  purpose 
it  is  added  to  albumen  and  certain  mountants.  Solubility :  1  in 
1 5  of  water,  5  in  1  of  alcohol,  4  in  1  of  ether. 

69 


Car] 


DICTIONARY  OF  PHOTOGRAPHY. 


Carbon  or  Autotype  Process.  One  of  the  most  permanent 
of  all  photographic  printing  processes.  Is  based  upon  the  fact 
that  a  mixture  of  gelatine  with  any  alkaline  bichromate  is 
rendered  insoluble  in  water  by  the  action  of  light.  By  in- 
corporating certain  colouring  matters  consisting  of  carbon  with 
various  other  pigments,  an  image  in  these  colours  can  be  ob- 
tained by  exposure  under  a  negative.  The  chemical  action 
which  takes  place  is  as  follows : — The  chromic  acid  of  the 
bichromate  is  reduced  to  a  lower  chromic  oxide  by  the  action  of 
organic  matter,  gelatine,  and  light,  and  this  combines  with  the 
gelatine  to  form  a  kind  of  leather.  The  process  of  preparing 
the  tissue  is  tiresome  and  dirty  on  a  small  scale  ;  the  prepared 
and  sensitised  paper  can  be  bought  at  about  the  same  rate  as 
ordinary  sensitised  paper.  When  sensitised,  the  paper  will  keep 
only  fourteen  days,  but  as  the  process  of  sensitising  is  com- 
paratively easy,  it  is  better  to  buy  the  unsensitised  tissue,  and 
sensitise  in  small  quantities  as  wanted.  The  colours  are  warm 
black,  engraving  black,  standard  brown,  standard  purple,  portrait 
brown,  portrait  purple,  sepia,  red  chalk,  and  special  transparency 
tissue  for  lantern  slides.  The  paper,  or  tissue,  as  it  is  called,  is 
sensitised  in  the  following  bath  : — 

Bichromate  of  potash  ...  I  oz.  or  30  grms. 
Liq.  ammon.  fort.  *88o  ...  5  drops  ,,  3  c.cm. 
Distilled  water    20  ozs.    ,,  500 

The  tissue  is  immersed  in  this  for  two  minutes  in  hot  weather 
and  three  minutes  in  cold.  It  must  be  dried,  and  kept  protected 
from  light,  air,  and  damp.  From  the  colour  of  the  tissue  it  is 
evident  but  little,  if  any,  image  can  be  seen;  therefore  the 
duration  of  exposure  is  judged  by  means  of  an  actinometer 
of  ordinary  chloride  albumenised  paper,  and  according  to  the 
density  of  the  negative  the  tissue  is  exposed  whilst  the  actino- 
meter registers  one,  two,  or  three  tints.  The  action  of  light 
continues  in  the  dark.  Allowance  must,  therefore,  be  made  for 
this  fact  if  the  tissue  is  not  to  be  developed  at  once.  As  the 
exposure  to  light  renders  the  gelatine  insoluble  (and  as  the 
action  of  development  is  to  remove  the  unacted-upon  gelatine), 
it  is  obvious  that  it  will  be  useless  to  try  and  develop  the  picture 
upon  the  face,  as  the  gelatine  is  insoluble  there.    It  must,  there- 

70 


DICTIONARY  OF  PHOTOGRAPHY. 


[Car 


fore,  be  transferred  to  some  support,  so  as  to  enable  the  gelatine 
to  be  dissolved  away  from  the  back,  for  which  purpose  the 
paper  must  be  removed ;  and  as  this  transfer  would  reverse  the 
print — i.e.,  make  the  right  hand  of  the  picture  the  left — when  a 
negative  taken  in  the  ordinary  way  is  used,  a  temporary  support 
is  required,  from  which  the  developed  print  is  again  transferred 
to  its  correct  position.  This  temporary  support  may  be  either 
a  mulled  zinc  plate,  glass,  or  a  specially  prepared  paper,  accord- 
ing to  the  surface  desired.  From  the  temporary  support  again 
the  print  may  be  transferred  to  any  substance — viz.,  paper,  opal 
glass,  porcelain,  metals,  ivory,  terra-cotta,  stone,  wood,  etc. 
The  special  transfer  paper  or  temporary  support  is  a  tough, 
smooth  paper  coated  with  shellac  and  rolled,  and  then  when 
required  for  use  it  is  waxed  to  prevent  the  gelatine  film  from 
adhering  permanently  to  it,  the  following  solution  being  used 
for  that  purpose  : — 

Yellow  resin   36  grs.  or  2  3  grms. 

Yellow  wax   12         ,,  -66  grm. 

Turpentine   ...    2  ozs.  ,,  59  c.cm. 

Melt  the  wax,  add  the  resin  and  turpentine.  The  writer  has 
found  the  substitution  of  ether  for  turpentine  a  decided  advantage, 
as  the  temporary  support  can  be  used  immediately ;  when 
turpentine  is  used  at  least  six  hours  must  elapse  after  the  waxing 
solution  has  been  applied  to  the  paper,  which  is  done  with  a 
tuft  of  cotton-wool,  or  flannel,  and  a  fresh  tuft  of  wool  being 
used  to  polish.  The  printed  tissue  and  the  waxed  temporary 
support,  of  whatever  nature  it  may  be,  are  immersed  in  cold 
water,  till  the  tissue  begins  to  uncurl  and  float  flat ;  it  is  brought 
into  contact,  film  side  downwards,  with  the  temporary  support, 
and  both  raised  together  from  the  water,  and  then  the  squeegee 
is  used  to  bring  them  into  optical  contact.  They  are  then 
placed  between  blotting  boards  for  five  or  ten  minutes,  and  then 
immersed  in  a  bath  of  water  at  a  temperature  of  1050  or 
no°  F.,  and  when  the  pigmented  gelatine  begins  to  ooze 
out  at  the  edges  of  the  paper,  strip  off  the  paper  upon  which  the 
gelatine  was  spread,  and  keep  washing  the  print  with  the  hot 
water  by  throwing  the  hot  water  on  to  it  with  the  hand,  or  by 
means  of  a  cup  or  soft  broad  brush,  or  a  small  sponge.    As  this 

7' 


Car] 


DICTIONARY  OF  PHOTOGRAPHY. 


is  done  it  will  be  found  that  the  gelatine  unacted  upon  by  light 
will  be  dissolved  away  with  the  colouring  pigment,  leaving  the 
print  in  all  its  beauty.  As  soon  as  development  is  complete  it 
is  plunged  into  a  bath  of  cold  water  to  set  the  gelatine,  and  then 
it  is  placed  in  a  bath  of  the  following  : — 

Powdered  alum    I  oz.  or  25  grms. 

Water    20  ozs.  „  500  ccm. 

This  not  only  fixes  the  print  by  hardening  the  gelatine,  but  it 
also  discharges  the  yellow  colour  of  the  bichromate  salt.  It  is 
allowed  to  remain  in  this  bath  for  about  ten  minutes,  or  till  the 
colour  is  entirely  discharged  from  the  whites  of  the  picture,  and 
finally  rinsed  twice  or  three  times  in  clear  water.  The  print  is 
now  ready  for  transferring  to  its  final  support,  of  whatever  nature 
that  may  be ;  but  before  this  transfer  can  take  place  it  is  necessary 
that  the  final  support  should  be  prepared  to  receive  it,  for  which 
purpose  it  is  coated  with  the  following  : — 

Nelson's  gelatine    1  oz.  or   25  grms. 

Water    20  ozs.  „  500  ccm. 

Soak  the  gelatine  in  the  water  for  an  hour,  or  till  soft,  and  then 
dissolve  by  the  aid  of  a  gentle  heat.  When  dissolved,  add 
to  it  gradually  12  grs.  of  chrome  alum  dissolved  in  1  oz.  of 
water.  The  commercial  final  support,  which  is  a  stout  paper, 
is  already  prepared,  and  merely  requires  soaking  in  alum  solu- 
tion, ^  oz.  to  the  pint,  an  hour  before  using.  The  print  on  its 
temporary  support  and  the  final  support,  whether  freshly  prepared 
or  not,  are  brought  into  close  contact  under  the  surface  of  water, 
and  optical  contact  obtained  by  means  ot  a  squeegee,  and  are 
then  placed  in  blotting  boards,  or  hung  up  till  perfectly  dry,  when 
the  temporary  support  can  be  stripped  off,  leaving  the  print  in  its 
proper  position.  It  is  advisable  for  any  amateur  who  may  wish 
to  work  in  carbon  to  obtain  Sawyer's  "ABC  Guide  to  Autotype 
Printing,"  in  which  everything  will  be  found  most  explicitly 
explained.  The  disadvantage  of  the  process  is  the  necessity 
for  the  use  of  reversed  or  film  negatives,  or  the  employment 
of  a  temporary  support.  The  advantages  are  the  absolute  per- 
manency of  the  pictures,  the  easy  manipulations  of  the  process, 
and  the  fact  that  prints  of  almost  any  colour  may  be  transferred 

72 


DICTIONARY  OF  PHOTOGRAPHY. 


[Car 


to  any  material,  and  the  resulting  pictures  can  be  retouched, 
spotted,  or  otherwise  worked  up  by  the  brush  in  the  same 
colour.  The  process  is  very  easy  and  simple,  and  the  materials 
so  cheap,  that  every  amateur  should  number  this  amongst  his 
photographic  processes.  Directions  have  been  given  for  double 
transfer  only.  Single  transfer  is  easier,  as  the  intermediate  or 
temporary  support  is  not  required.  Reversed  negatives,  how- 
ever, must  be  used,  and  the  print  is  developed  in  precisely  the 
same  manner  as  directed  on  pp.  71  and  72.  When  developed, 
it  is  transferred  at  once  to  its  final  support,  which  must  be  pre- 
pared with  solution  of  gelatine  as  directed  on  p.  72.  The  trans- 
ferred print  is  then  well  washed  in  water  and  soaked  in  the  alum 
bath  (p.  72),  and  reared  up  to  dry  after  another  washing.  On  p.  70 
it  is  stated  that  "  the  action  of  light  continues  in  the  dark."  Some 
doubt  has  been  thrown  on  this,  but  it  is  an  acknowledged  fact 
that  the  action  of  light  is  continued  in  a  damp  atmosphere. 
The  following  are  some  of  the  principal  pigments  used  in 
carbon  work  ;  for  the  formulae  I  am  indebted  to  the  "  Year 
Book  of  Photography"  for  1889.  The  jelly  is  first  made  as 
follows  : — 

Nelson's  transparent  sheet  gelatine        ...      10  parts. 

White  sugar   ...       ...       ...       4  ,, 

Water    25  ,, 

Soak  the  gelatine  in  the  water  until  soft,  and  dissolve  by  the  aid 
of  a  gentle  heat ;  add  the  sugar,  and  stir  thoroughly.  When  set, 
turn  the  jelly  out,  and  cut  off  the  bottom  part,  so  as  to  get  rid 
of  any  grit  that  may  have  settled  down.  A  good  photographic 
purple  brown  is  made  as  follows  : — 

Vegetable  black    72  grs.  or  5  grms. 

Alizarine  lake    60    „    ,,  4 

Indigo    13    ,,    ,,  1  „ 

Grind  these  with  about  4  ozs.  of  melted  jelly,  using  muller  and 
slab,  and  add  to  6  lbs.  of  the  above-mentioned  jelly. 


Black  Tissue. 


Jelly  

Paris  black  pigment 


2  lbs.  or  1,000  grms. 
50  grs.  ,,         3  „ 


73 


Car]  DICTIONARY  OF  PHOTOGRAPHY. 

Red  Chalk  or  Bartolozzi. 

Jelly   2  lbs.  or  1,000  grms. 

Venetian  red    3  ozs.  „       75  „ 

Indian  ink    8  grs.  „        -5  grm. 

Transparency  Tissue. 

Jelly   2  lbs.  or  1,000  grms. 

Indian  ink    200  grs.  ,,       12  ,, 

To  make  Double  Transfer  Paper. 

Hard  gelatine    1   lb.   or  500  grms. 

Fine  sulphate  of  baryta     ...       8  oz.    ,,  250  „ 

Water    5    M     „  150  ,, 

Soak  the  gelatine  till  soft,  and  dissolve  by  the  aid  of  heat ;  mix 
the  baryta,  and  add 

Chrome  alum    50  grs.  or        3  grms. 

dissolved  in 

Water    4  ozs.    „    100  „ 

For  Single  Transfer  Paper. 

Hard  gelatine    1  lb.    or    500  grms. 

Water    5  pints 2.5  litres. 

Soak  the  gelatine,  and  dissolve  by  heat,  and  add 

Chrome  alum    300  grs.    or    20  grms. 

Water    1  pint    „   500  c.cm. 

This  will  make  the  mixture  thick  and  ropy,  and  sufficient  acetic 
acid  should  be  added  to  make  it  liquid.  A  convenient  little  work 
on  the  preparation  of  these  papers  is  "  The  Carbon  Process,"  by 
the  author. 

Carrier.  A  framework  of  wood  used  in  dark  slides  to  enable 
the  operator  to  use  smaller  plates  than  those  for  which  the 
camera  was  designed. 

Carte  de  Visite.  Usually  the  smallest  size  of  the  professional 
photograph,  measuring  about  4  by  2  J  ins. 

74 


DICTIONARY  OF  PHOTOGRAPHY. 


[Chr 


Castile  Soap  (Ger.,  Seife;  Fr.,  Savon;  Ital.,  Safione). 
Synonyms :  Hard  Soap,  White  Castile  Soap.  A  white,  or 
greyish  white,  soap  made  from  soda  and  olive  oil.  It  is  soluble 
in  rectified  spirit  and  in  hot  water.  It  is  used  as  a  lubricant 
for  burnishing.  Common  Castile  soap  is  veined  or  marbled 
with  an  iron  salt,  and  when  freshly  prepared  is  yellowish  white 
with  bluish  green  streaks.  When  old  the  iron  salt  turns  red. 
This  should  not  be  used. 

Catalysotype.  An  old  process  invented  by  a  Dr.  Woods,  in 
which  paper  was  impregnated  with  syrup  of  iodide  of  iron,  and 
then  painted  with  a  solution  of  nitrate  of  silver.  It  ,was  then 
exposed  in  the  camera  and  the  image  gradually  appeared. 

Chloroform  (Ger.,  Chloroform;  Fr.,  Chloroformc ;  Ital., 
Chloroformio).  CHC13.  Prepared  by  the  action  of  free 
chlorine  on  alcohol  or  methylated  alcohol.  It  is  a  heavy, 
colourless  liquid  of  pleasant  smell  and  sweet,  hot  taste.  It 
dissolves  in  alcohol  and  ether  in  all  proportions,  and  i  volume 
in  200  of  water.  It  evaporates  very  quickly,  and  leaves  no 
residue.    It  is  used  in  some  varnishes. 

Chlorophyll  (Ger.,  Chlorophyll  or  Blattgrun ;  Fr.,  Chloro- 
phylle  ;  Ital.,  Clorofilla  or  Cromolo).  This  is  the  green  colouring 
matter  of  plants  and  leaves,  and  is  stated  to  be  composed  of 
two  substances,  phylloxanthine,  of  a  yellow  colour,  and  phyllo- 
cyanine,  which  is  blue.  It  is  slightly  soluble  in  water,  but  more 
so  in  alcohol  and  ether.  It  has  been  used  for  sensitising  plates 
for  ortho-chromatic  work,  and  for  this  purpose  either  ivy,  parsley 
or  blue  myrtle  (periwinkle,  vinca  major)  should  be  used.  The 
fresh  leaves  should  be  cut  up  small  and  rubbed  in  a  mortar,  and 
then  allowed  to  macerate  in  alcohol  for  24  hours.  Chlorophyll 
solutions  do  not  keep  well,  but  a  fragment  of  zinc  in  the  bottle 
helps  to  keep  it  better. 

Chromatic  Aberration.  When  light  passes  through  a  prism 
or  a  lens,  which  may  be  considered  as  formed  of  prisms,  it  is 
broken  up  or  refracted  into  its  constituent  rays.  If  a  ray  of  light, 
rr,  strike  a  lens  l,  it  is  refracted  and  dispersed,  and  as  the 
violet  rays  are  bent  out  of  their  course  more  than  the  red,  it  is 
obvious  that  they  will  meet  at  a  point  nearer  the  lens  than  the 
red  ones,  as  shown  in  the  figure.   Therefore,  suppose  we  wish  to 

75 


Chr] 


DICTIONARY  OF  PHOTOGRAPHY. 


get  an  image  .of  the  object  from  which  rr  proceeds,  and  place  a 
screen  at  V>  we  shall  see  a  violet  image  surrounded  by  rings  of 
blue,  green,  orange,  yellow  and  red.  And  by  placing  the  screen 
at  Y>  we  shall  get  a  red  image  surrounded  by  orange,  yellow, 
green,  blue  and  violet  rings,  and  this  will  be  the  case  at  each  point 
where  the  different  coloured  rays  cross  the  axis,  though  for  the 
sake  of  clearness  these  are  not  shown.  Now  the  brightest  part  of 
the  spectrum  to  the  human  eye  is  in  the  yellow,  whilst  the  rays 
which  act  most  on  the  plate  are  in  the  blue  and  violet,  so  that  if 


31  £ 

;  » 

\ 

x  1 

X 

B 

X 

Fig.  7. 


we  obtain  an  image  by  the  yellow  rays,  the  plate  would  be 
affected  by  the  blue  and  violet,  and  we  should  get  no  sharp 
picture,  because  at  Y  the  blue  rays  would  be  a  circle  instead  of 
a  point.  This  is  termed  non-coincidence  of  the  visual  and 
chemical  foci,  or  the  lenses  are  said  to  be  uncorrected  or  non- 
achromatic.  Now  it  is  a  fact  that  crown  and  flint  glass  have 
different  dispersive  powers,  that  is,  they  produce  spectra  which 
differ  in  the  position  of  the  Fraunhofer  lines.  With  the  crown  glass 
the  distances  between  a  b  and  B  c,  in  the  red  and  orange,  is 
greater  than  with  the  flint,  whereas  with  the  flint  the  distances 
between  f  g  and  g  h  are  greater  than  with  the  crown.  Therefore 

76 


DICTIONARY  OF  PHOTOGRAPHY. 


[Chr 


we  may  assert  that,  with  the  crown  glass,  the  red  end  or  less 
refrangible  rays  are  extended  at"  the  expense  of  the  violet  or 
more  refrangible  rays,  whilst  with  the  flint  glass  the  opposite 
holds  good.    We  have  seen  that  we  have  a  lens  which  is 


Fig.  8. 


practically  a  collection  of  prisms;  we  have  also  seen  that  the 
visual  and  chemical  rays  do  not  have  the  same  focus,  and  it  is 
essential  they  should  possess  this  in  common.  Light  is  always 
refracted  towards  the  base  of  a  prism,  and  we  have  just  pointed 


>-  > 

Fig.  9- 

out  that  flint  and  crown  glass  act  differently  on  the  spectrum, 
the  one  extends  the  blue,  the  other  the  red  end  more,  so  that 
it  is  not  difficult  to  see  from  fig.  8,  that  what  we  want  to  do  is 
to  make  /fall  upon  /'.  This  represents,  exaggerated  of  course, 
the  action  of  a  convex  crown-glass  lens.  Now,  suppose  we 
examine  the  action  of  a  concave  flint-glass  lens.    In  this  case, 

77 


Chr] 


DICTIONARY  OF  PHOTOGRAPHY. 


fig.  9,  it  is  seen  that  the  blue  rays  are  bent  out  more  than 
the  yellow,  so  that,  if  we  combine  a  flint  concave  with  a  crown 
convex,  we  shall  get  the  blue  rays  extended  more,  and  thus 
neutralise  the  effect  of  the  crown  to  some  extent.  I  endeavour 
to  show  this  in  fig.  10.  The  focus  of  the  crown  lens  is  shown 
at  2  for  the  yellow  rays  and  at  I  for  the  blue ;  but  by  adding 


Fig.  10. 


a  concave  flint,  the  focus  of  both  is  lengthened  to  f.  Now, 
there  are  more  rays  than  the  blue  and  yellow  in  the  spectrum, 
and  it  naturally  occurs  to  ask  about  the  others ;  these  are  left 
outstanding,  and  at  /  form  coloured  rings  round  the  central 
spot  or  sharp  focus  f,  and  form  what  is  called  the  secondary 
spectrum.     In  the  last  figure  we  only  used  two  lenses,  but 


Fig.  ii. 


if  we  use  three,  three  rays  are  combined  and  the  lens  is  said 
to  be  apochromatic,  and  the  faint  outstanding  rays  of  colour 
are  called  the  residuary  tertiary  spectrum.  The  advantage  of 
the  more  perfect  achromatism  of  lenses  at  the  present  time 
is  shown  from  the  following  statement.  The  ordinary  gelatino- 
bromide  plate  is  sensitive,  not  only  to  those  particular  portions 
of  the  spectrum  designated  by  d  and  f,  but  also  between  d  and  f. 

78 


DICTIONARY  OF  PHOTOGRAPHY. 


[Cle 


and  f  and  h;  and  if  we  use  colour-sensitive  plates,  we  find 
considerable  increase  of  sensitiveness  to  the  yellowish  green 
about  E,  so  that  those  rays  for  which  the  lens  is  not  perfectly 
achromatised  may  act,  and  as  these  rays  do  not  form  an  exact 
image  at  that  point  where  d  and  f  meet,  they  may  affect  the 
silver  in  such  a  manner  as  to  enable  the  developer  to  reduce 
the  same  ;  and  although  such  reduction  would  be  hardly  visible 
to  the  naked  eye,  yet,  in  enlarging,  the  points  of  confusion  thus 
caused  might  become  visible,  and  give  indistinctness  or  fuzziness. 

Chrome  Alum.   See  Alum. 

Chrysotype.   An  obsolete  process. 

Circle  of  Least  Confusion.  An  optical  term  to  denote  the 
nearest  approach  to  an  absolute  focus  of  an  oblique  pencil  of 
light  after  refraction. 

Citric  Acid  (Ger.,  Citronensdure ;  Fr.,  Acide  citriqicc ;  Ital., 
Acido  Citrico).  HQH507,  H20  =  208.  Occurs  naturally  in  the 
juice  of  many  fruits,  and  is  obtained  chiefly  from  the  lime  and 
lemon  juice  by  heating  and  adding  chalk,  collecting  the  precipitate 
and  decomposing  with  sulphuric  acid,  and  evaporating  the  solution 
till  crystals  are  obtained.  Solubility:  133  per  cent,  in  cold, 
200  per  cent,  in  hot  water,  soluble  in  alcohol  and  ether.  It  is 
used  to  make  citrates,  as  an  ingredient  of  clearing  solutions,  and 
as  a  preservative  for  sensitised  paper. 

Clearing  Bath.  Any  solution  used  to  clear  or  cleanse  a 
negative  or  positive  from  the  stains  of  development  is  thus 
termed.    The  following  are  those  in  most  common  use  : — 

Alum   2  ozs.  or  50  grms. 

Citric  acid    1  oz.   ,,    25  ,, 

Water    20  ozs.  ,,  500  c.cm. 


The  latter  is  the  author's  favourite,  the  chrome  alum  having  a 
special  tanning  action  on  the  film  much  superior  to  ordinary  alum. 
The  addition  of  a  little  ferrous  sulphate  has  been  recommended, 


Or 


Chrome  alum 
Citric  acid  . 
Water 


1  oz.  or  25  grms. 
1  »    m    25  „ 
20  ozs.  ,,  500  c.cm. 


79 


Cli] 


DICTIONARY  OF  PHOTOGRAPHY. 


but  without  any  increased  benefit.  When  plates  are  developed 
by  pyrogallol  and  soda,  a  very  non-actinic  yellow  colour  is  given 
to  the  film,  which  protracts  the  operation  of  printing  most  in- 
ordinately. By  use  of  the  chrome  alum  bath  this  colour  is 
changed  to  fine  olive  green,  which  does  not  protract  printing. 
In  the  case  of  ferrous-oxalate  development  the  same  bath  is 
useful  for  clearing  off  the  deposit  of  oxalate  of  lime  due  to  the 
use  of  hard  water,  whether  on  negatives,  positives,  opals,  or 
paper.  Mr.  B.  J.  Edwards  has  suggested  the  following,  which, 
as  it  possesses  one  or  two  features  distinct  from  the  others,  is 
here  given : — 

I. 

Alum   I  oz.  or  28  grms. 

Citric  acid    1  ,,        28  „ 

Water   15  „   M  400  c. cm. 

II. 

Saturated  solution  of  sulphate  of  iron  ...  5  ozs.  or  145  c.cm. 

For  ordinary  use  one  part  No.  II.  is  mixed  with  three  parts  of  No.  I. 
If  the  negative  is  a  little  too  dense,  the  use  of  No.  I.  solution 
alone  will  reduce  the  same.  If  not  quite  dense  enough,  the  use 
of  No.  II.  alone  will  often  give  the  slight  snap  required  to  pro- 
duce a  perfect  negative.  Mr.  Edwards  recommends  the  use  of 
this  clearing  bath  immediately  after  fixing,  the  plate  being  only 
just  rinsed  after  being  taken  out  of  the  fixing  bath.  The 
following  solution  has  been  specially  recommended  for  removing 
pyro  stains  and  is  very  effectual : — 

Thiocarbamid    30  grs. 

Citric  acid    ...       ...       ...       ...       ...  10 

Water    5  ozs. 

Cliche.  A  term  applied  to  the  negatives  and  moulds  used  in 
photo-mechanical  printing. 

Cloud  Negatives.  There  are  few  landscapes  or  seascapes 
taken  by  amateurs  which  would  not  be  improved  by  the  addition 
of  clouds — in  fact,  in  many  instances  an  otherwise  poor  print 
may  be  made  a  picture  by  the  judicious  use  of  the  same.  It 
must,  however,  be  borne  in  mind  that  clouds  which  are  unsuit- 

80 


DICTIONARY  OF  PHOTOGRAPHY.  [ClO 

able  to  the  landscape,  or  which  are  differently  lighted,  are  worse 
than  a  blank  sky.  For  taking  cloud  negatives  it  will  be  found 
that  slow  or  medium  plates,  rich  in  silver  and  preferably  coated 
with  a  bromo-iodide  emulsion,  will  answer  well ;  but  the  finest 
effects  will  be  obtained  by  the  use  of  isochromatic  or  orthochro- 
matic  plates,  with  a  yellow  screen  interposed  between  the  lens 
and  plate.  The  majority  of  landscape  photographs  have  the 
horizons  from  one-third  to  two-thirds  up  the  plate ;  therefore  it 
would  not  be  advisable  to  point  the  lens  to  the  zenith  to  obtain 
cloud  negatives,  as  the  lighting,  as  a  rule,  is  different  to  that  ob- 
tained nearer  the  horizon.  It  will  be  found  that  good  cloud 
scenes  may  be  obtained  without  much  difficulty  from  any  open 
space  near  London  or  any  other  city  or  town  ;  and  the  author 
has  obtained  very  fine  negatives  from  the  upper  windows  of  an 
ordinary  dwelling  house,  and  in  practice  he  makes  it  a  rule,  if 
possible,  to  include  some  of  the  housetops  or  distant  landscape 
in  the  field  of  view,  though  this  is  totally  disregarded  in  exposure 
and  development.  The  lens  used  may  be,  of  course,  that  usually 
employed,  and  it  should  be  racked  out  to  its  equivalent  focus, 
and  a  comparatively  small  diaphragm  used — though  this  will 
depend  upon  the  character  of  the  clouds,  as  heavy,  dark  thunder- 
clouds will  require  a  larger  aperture  than  the  fleecy  clouds  of 
bright  weather.  For  dark  masses,  as  a  rule,//22  will  be  large 
enough ;  whilst  for  bright  sunlit  masses  on  a  blue  sky  as  small 
as  //64  will  be  found  ample.  In  any  case,  however,  a  shutter 
exposure  will  be  required ;  generally  from  £  to  ^  sec.  will  be 
sufficient.  For  development  of  such  plates  it  is  advisable  to 
keep  down  pyro,  so  as  to  obtain  soft  and  delicate  negatives 
rather  than  bold  or  vigorous  contrasts,  and  the  development 
should  not  be  pushed  too  far.  For  sunrise  and  sunset  effects 
isochromatic  plates  are  a  sine  qua  non  ;  these  alone  will  in  any 
way  do  but  tardy  justice  to  the  sometimes  beautiful  effects  to  be 
obtained  at  these  times  ;  but  in  every  case  it  must  not  be  forgotten 
that  colour  must  be  disregarded,  shape  and  the  relative  massing 
of  the  clouds  alone  being  of  any  use  to  the  photographers.  To 
print  clouds  into  a  negative  it  is  advisable  first  to  take  a  print  on 
ordinary  albumenised  paper,  and  then  the  outline  of  the  sky 
should  be  carefully  cut  with  a  sharp  pair  of  fine-pointed  scissors, 
and  this  mask,  as  it  is  termed,  should  be  adjusted  on  the  negative, 
and  the  sky  printed  in  on  the  print  after  the  landscape  or  sea- 

8l  G 


Col] 


DICTIONARY  OF  PHOTOGRAPHY. 


scape  has  been  printed.  For  printing  clouds  in  enlargements 
and  lantern  slides  the  same  plan  may  be  adopted,  or  with  the 
latter  the  clouds  may  be  printed  on  another  plate,  and  the  same, 
when  developed,  fixed,  and  washed,  used  as  a  covering  glass. 
In  the  finished  print  clouds  should,  in  almost  every  case,  be 
subordinate  to  the  landscape,  and  therefore  they  should  not  be 
so  heavily  printed — in  fact,  in  some  cases  the  merest  suspicion 
of  clouds  is  quite  sufficient  to  produce  an  artistic  effect. 

Collodio-Chloride  Printing-out  Paper.  This  was  first 
proposed  by  Wharton  Simpson  in  1865,  and  for  some  consider- 
able time  it  was  a  very  favourite  printing  process.  It  gradually 
fell  into  disuse,  but  has  lately  been  revived.  Numerous  formulae 
have  been  suggested,  but  the  three  following  will  be  found  to  yield 
good  results. 


Monckhoveris  Formula. 
A.    Plain  Collodion. 

Pyroxyline   1  part. 

Ether     10  parts. 

Alcohol      10  ,, 


B. 

Magnesium  chloride  (cryst.)    1  part. 

Alcohol   ...      10  parts. 

Filter. 

C 

Silver  nitrate    2  parts. 

Boiling  dist.  water    3  ,, 

Alcohol    7  m 

Dissolve  the  silver,  previously  powdered  in  the  water,  then  add 
the  alcohol. 

D. 

Citric  acid    2  parts. 

Boiling  dist.  water    2  „ 

Alcohol    16  ~ 

82 


DICTIONARY  OF  PHOTOGRAPHY. 

To  make  the  emulsion,  take  of 

Solution  A  

and  add  gradually,  with  constant  shaking 

Solution  B  

Then  in  the  same  manner 

Solution  C  

and  finally 

Solution  D.  ... 


[Col 


60  parts, 

5  parts. 

6  parts, 
4  parts. 


The  emulsion  should  be  allowed  to  stand  at  least  eight  days,  and 
it  works,  if  anything,  better  in  six  months. 


Licscgangs  Formula. 
A. 


Silver  nitrate 
Alcohol 


2  parts 
100  .. 


Strontium  chloride 
Alcohol 


2  parts. 
100  .. 


Citric  acid   

Alcohol   

D. 

Pyroxylin   

Ether   

Alcohol   

To  make  the  emulsion  take  of 

Solution  D  

„      C  ... 

B  

Mix  well  and  add  gradually,  with  constant  shaking, 


Solution  A 


83 


2  parts. 
100  ,, 


4  parts. 
100  „ 
100  .. 


100  parts. 
10 
10 


5  parts. 


Col] 


DICTIONARY  OF  PHOTOGRAPHY. 


The  emulsion  should  be  allowed  to  stand  three  days.  The 
following  is  the  one  which  has  given  us  the  best  results. 

Geldmache^s  Formula  {modified). 
A. 

Schering's  Celloidin    20  parts. 

Ether   ...   400    , , 

Alcohol   400 

Castor  oil    4  „ 

B. 

Silver  nitrate    20  parts. 

Distilled  water    20  „ 

Alcohol    50  „ 

C. 

Citric  acid      5  parts. 

Alcohol    70  ,, 

D. 

Lithium  Chloride    25  parts. 

Strontium  Chloride   2.5  „ 

Alcohol    70  it 

Mix  solutions  C  and  D  and  add  gradually  to  the  collodion,  and 
then  add  B  very  gradually  with  constant  shaking,  and  finally  5 
parts  of  pure  glycerine.  The  emulsion  should  now  be  allowed  to 
stand  for  six  hours.  Baryta  or  Kreide  paper  is  always  used  as 
the  support,  and  the  edges  of  a  sheet  are  turned  up,  the  paper 
laid  on  a  sheet  of  plate  glass,  and  coated  with  the  collodion  just 
the  same  as  though  it  were  the  glass  itself.  It  is  then  allowed  to 
set  and  dry.  It  is  printed  in  just  the  same  way  as  any  ordinary 
gelatino-chloride  paper,  and  may  be  treated  and  toned  in  the  same 
way ;  but  it  will  be  found  that  the  paper  is  very  apt  to  curl  up  in 
the  solutions.  This  may  be  avoided  by  laying  the  print  on  the 
bottom  of  an  empty  dry  dish,  and  pouring  very  hot  water  on  to 
the  collodion  film,  allowing  it  to  soak  for  a  minute  and  then 
washing  thoroughly,  either  in  plain  water  or  salt  water,  as  suggested 
for  gelatino-chloride  paper.  The  best  results  are  obtained  with 
the  simple  sulphocyanide  bath.     The  only  precaution  to  be 

84 


DICTIONARY  OF  PHOTOGRAPHY. 


[Col 


observed  in  the  use  of  this  paper  is  that,  if  bent  sharply  across,  it 
will  crack. 

Collodion.  The  vehicle  used  in  wet-plate  processes  for 
holding  the  haloid  salts  necessary  for  the  formation  of  the 
sensitive  salts  of  silver.  It  is  prepared  by  dissolving  Pyroxyline 
{q.v.)  in  a  mixture  of  equal  parts  of  alcohol  and  ether.  It  is  a 
transparent  glutinous  liquid,  which,  when  poured  upon  any  sur- 
face, leaves,  by  the  evaporation  of  the  solvents,  an  attenuated 
film  of  pyroxyline  absolutely  transparent  and  structureless,  well 
adapted  for  the  purpose  for  which  it  is  required.  The  usual 
strength  is  as  follows  : — 

Pyroxyline   5  grs.  or     -3  grm. 

Alcohol,  820  sp.  gr.          ...       \  oz.    „  12-5  c.cm. 
Ether,  725  sp.gr   |  „     „  12-5  „ 

Methylated  alcohol  and  methylated  ether  may  be,  and  are, 
chiefly  used  on  account  of  their  cheapness.  A  special  kind  of 
collodion,  called  enamel  or  leather  collodion,  is  used  for 
enamelling  Prints  {q.v.). 

Collotype.  Synonyms  :  Albertype,  Artotype,  Phototype.  Col- 
lotype is  a  photomechanical  process  by  which  prints  in  greasy  ink 
are  obtained  by  means  of  a  film  of  gelatine  in  relief.  Briefly  the 
process  is  summed  up  as  follows  :  a  film  of  gelatine  containing  a 
bichromate  salt  is  exposed  to  light  under  a  negative,  washed, 
dried  off,  and  inked  with  greasy  ink,  which  adheres  only  to  those 
places.which  have  been  affected  by  light.  By  using  a  suitable  press 
innumerable  proofs  can  be  obtained.  Negatives  for  preparing 
the  collotype  plates,  as  they  are  called,  must  be  reversed 
(see  Reversed  Negatives),  and  should  be  of  a  rather  soft, 
delicate  character,  free  from  yellow  stain.  They  should  also  be 
provided  with  a  safe  edge  which  is  usually  made  of  tin  foil.  It 
is  customary  to  prepare  several  negatives  of  one  subject  when  a 
large  number  of  pulls  or  prints  is  required  ;  as  many  as  two,  four, 
six,  or  eight,  bring  prepared  at  once,  on  sheets  of  plate  glass,  which 
should  be  about  fths  inch  thick ;  the  edges  and  corners  should  be 
ground  off.  This  glass  is  grained,  and  it  is  usual  to  grain  two  at 
once  by  placing  some  emery  flour  moistened  with  water  on  one, 
which  should  be  laid  absolutely  flat  on  a  table,  and  placing 
another  plate  on  top,  and  working  this  about  till  both  surfaces 

85 


Col] 


DICTIONARY  OF  PHOTOGRAPHY. 


are  evenly  grained ;  care  being  exercised  to  keep  the  emery 
moist.  As  soon  as  the  surfaces  are  ground,  the  emery  is  washed 
off  and  finer  emery  flour  used  in  the  same  way  till  the  surfaces 
look  perfectly  homogeneous  and  free  from  deep  pits  or  scratches. 
The  plates  are  then  thoroughly  washed,  rinsed  in  distilled  water, 
and  set  up  to  drain.  To  ensure  adherence  of  the  gelatine  to  the 
glass  during  the  hard  usage  to  which  it  is  subjected  in  printing 
a  substratum  is  used.  This  is  usually  a  mixture  of  beer  and 
silicate  of  soda  or  potash.  The  beer  to  be  used  is  that  known  as 
"  four  ale,"  which  should  be  allowed  to  stand  twenty-four  hours 
to  get  perfectly  flat.    The  mixture  is 

Four  ale   200  parts. 

Silicate  of  soda  (sirupy)    10  „ 

This  mixture  is  well  stirred,  allowed  to  stand  for  some  time,  and 
then  filtered  through  nainsook,  well  washed  previously,  and  it  is 
ready  for  use.  The  plates  are  heated  gently  in  a  collotype  drying 
oven,  and  then  rinsed  with  a  little  weak  ammonia  water,  and 
allowed  to  dry  ;  or  else,  after  being  dusted,  they  are  flowed  over 
with  the  silicate  mixture,  the  excess  being  allowed  to  run  off  into 
the  sink,  drained  for  a  minute,  and  a  second  coating  given  them, 
when  they  are  placed  in  the  oven  in  which  they  very  soon  dry. 
Another  substratum,  lately  recommended  by  Holzhausen  and 
Wetherman,  is 

No.  1. 

Dextrine      40  parts. 

Sugar  ..    5  ,, 

Alcohol    5  „ 

Water      40  „ 

No.  2. 

Silicate  of  potash  (liquid)  1200  parts. 

Tannin        ...       ...       ...       ...       ...     2*5  „ 

Dissolve  the  dextrine  and  sugar  in  the  water,  and  add  the  alcohol. 
Dissolve  the  tannin  in  a  small  quantity  of  water,  mix  with  the 
silicate,  allow  to  stand  for  twenty-four  hours.  Both  solutions  will 
keep  some  time  separate.    For  use  take 

No.  1  ...    1  part. 

No.  2   2  parts. 

Water     '     7  „ 

86 


DICTIONARY  OF  PHOTOGRAPHY.  [Col 

Filter  through  cloth.  This  must  be  used  at  once  as  it  will 
not  keep.  The  plate  should  be  placed  on  a  levelling  stand, 
and  after  brushing,  plenty  of  the  solution  should  be  poured 
on  and  spread  evenly  over,  ii  necessary  using  a  small  piece  of 
paper,  then  drain  oft  and  place  in  a  rack  to  dry ;  when  dry  the 
plates  should  be  well  rinsed  to  get  rid  of  the  free  silicate,  and 
again  dried,  and  the  plates  are  then  ready  for  coating.  The 
plates  may  also  be  dried  in  the  oven,  being  placed  on  edge,  and 
leaving  the  door  open,  and  regulating  the  heat  to  about  ioo°  F. 
The  sensitive  coating  is  bichromated  gelatine  prepared  as  fol- 
lows : — Special  collotype  gelatine,  80  parts  are  allowed  to  soak  in 
water  for  a  quarter  of  an  hour,  the  water  poured  off  and  as  much 
as  possible  squeezed  out ;  the  gelatine  is  then  placed  in  a  graduated 
measure,  and  water  added  to  1000  parts.  The  gelatine  is  melted  by 
the  aid  of  a  waterbath,  and  then  16  parts  of  bichromate  of  potash 
finely  powdered  are  added  and  dissolved  by  careful  stirring.  The 
mixture  is  then  filtered,  and  8  parts  of  ammonia  added,  drop  by 
drop,  till  the  solution  turns  a  yellowish  orange.  The  glass  is 
now  carefully  levelled  in  the  oven  and  heated,  and  the  plate 
carefully  and  evenly  coated,  from  100  to  120  minims  being 
allowed  for  about  4  ins.  square  of  glass.  The  plate  or  plates 
having  been  coated,  the  oven  is  closed  and  the  temperature 
allowed  to  attain  about  1150  F.,  and  this  temperature  must  be  kept 
even  during  the  whole  time  the  plates  are  drying ;  and  the  oven 
should  not  be  opened  till  the  plates  are  quite  dry,  which  at  the 
above  temperature  will  be  in  two  or  three  hours.  At  the  end  of 
this  time  the  gas  under  the  oven  should  be  turned  out  and  the 
plates  allowed  to  cool.  The  plates  when  cool  are  ready  for 
exposure,  and  this  is  effected  in  one  of  the  heavy  printing  frames 
with  plate-glass  front,  and  with  screw-bars  to  obtain  pressure. 
The  duration  of  exposure  is  sometimes  judged  by  examining  the 
plates  from  the  back,  but  the  safest  way  is  to  use  an  actinometer» 
using,  as  the  sensitive  paper  for  the  same,  a  piece  of  paper 
coated  with  the  same  mixture  as  used  for  the  plates.  A  little 
experience  soon  determines  the  number  of  tints  required  for  the 
particular  class  of  negative.  After  exposure  the  plate  is  removed, 
placed  face  downwards  on  a  sheet  of  black  cloth  or  paper,  and  the 
back  exposed  to  the  light ;  the  reason  for  this  being  to  cause 
perfect  adherence  to  the  glass,  and  to  lessen  the  relief,  which 
takes  but  a  short  time  and  may  be  determined  by  the  photometer 

87 


Col] 


DICTIONARY  OF  PHOTOGRAPHY. 


or  by  the  plate  assuming  a  brown  colour.  The  plate  is  then 
washed  for  some  hours  in  running  water,  or  till,  on  placing  on  a 
sheet  of  white  paper,  it  has  quite  lost  its  yellow  colour,  and  is 
then  dried  and  ready  for  printing,  or  may  be  kept  in  this  condition 
for  a  long  time.  For  printing,  the  plate  is  placed  absolutely 
horizontal,  and  covered  with  a  solution,  which  is  called  the 
etching  solution. 

Water    300  parts. 

Glycerine     ...       ...       ...       ...       ...  600  ,, 

Ammonia    30  „ 

Salt   ...     30  „ 

This  is  allowed  to  act  till,  on  passing  the  finger  gently  over  the 
surface  of  the  plate,  the  high  relief  has  disappeared.  The  solution 
is  then  poured  off,  and  the  excess  removed  with  a  soft  sponge, 
and  the  plate  is  then  rather  sharply  dabbed  with  a  cloth  or  fine 
blotting  paper.  The  plate  is  now  ready  for  fixing  on  the  machine, 
which  may  be  either  the  hand  or  steam  press.  A  mask  of  stout 
waxed  paper  is  cut  and  mounted,  so  as  to  cover  the  margins,  and 
the  plate  is  then  inked  and  printed  from.  The  inking  is  usually 
effected  with  two  rollers — the  one  of  leather  which  is  used  with 
a  thick  ink  and  heavy  pressure  to  ink  the  shadows,  and  the  other 
a  gelatine  roller  with  a  thinner  ink  and  lighter  pressure  for  the 
half-tones.  The  paper  on  which  the  proofs  are  pulled  may  be  of 
various  kinds.  It  may  be  glazed  or  unglazed,  rough  or  smooth 
surface,  India,  China,  or  Whatman's,  according  to  the  result 
desired,  and  the  proofs  may  be  allowed  to  dry  without  further 
treatment,  or  they  may  be  glazed,  which  is  usually  effected  by 
floating  the  prints  on  an  aqueous  solution  of  white  lac,  or  by 
coating  them  with  a  brush  with  label  varnish,  and  drying 
by  the  heat  of  a  gas  stove,  when  they  present  the  appear- 
ance of  ordinary  albumen  prints.  The  lac  varnish  is  made  by 
mixing  60  parts  of  white  lac  with  500  parts  of  water ;  60  parts  of 
borax  are  dissolved  in  700  parts  of  water,  and  the  two  solutions 
brought  to  the  boiling  point.  The  borax  is  added  gradually  to 
the  other,  and  the  mixture  boiled  for  some  minutes,  and  2  parts 
of  Marseilles  soap  dissolved  in  12  parts  of  alcohol  with  one  or 
two  drops  of  olive  oil  added,  with  800  parts  of  water ;  the  whole 
is  well  mixed,  allowed  to  settle,  and  cooled.    The  prints  are 


DICTIONARY  OF  PHOTOGRAPHY. 


[Com 


floated  on  this  in  exactly  the  same  way  as  for  sensitising 
albumen  paper  for  some  seconds,  and  then  allowed  to  dry.  The 
label  varnish  is  a  commercial  article,  or  may  be  prepared 
with 

Mastic    ...       ...       ...      30  parts. 

Oil  of  Lavender      ...       ...       ...       ...       5  ,, 

Alcohol        ...    150  ,, 

Benzine       ...       ...       ...       ...       ...     40  ,, 

this  is  allowed  to  stand  for  eight  days  with  occasional  agitation, 
and  then  decanted.  This  should  only  be  applied  to  collotypes 
on  chromo  or  baryta  paper,  and  should  be  applied  with  a  broad 
brush,  and  the  prints  dried  in  an  oven  or  drying  box  of  particular 
construction.  Grained  copper,  zinc  and  lead  plates  have  also 
been  used  instead  of  glass  for  the  support,  but  have  not  found 
much  application  commercially.  Flexible  supports  have  also  been 
used,  and  the  necessary  materials  and  apparatus  may  be  obtained 
commercially. 

Colour,  Effect  of,  in  Photography.  See  Isochromatic 
Photography. 

Colouring  Photographs.  An  operation  that  requires  con- 
siderable artistic  skill  and  ability.  The  subject  is  much  too 
comprehensive  to  be  treated  fully  here.  Water  colours  have 
a  decided  objection  to  adhere  to  the  glossy  surface  of  an  albu- 
menised  print,  but  they  may  be  made  to  do  so  by  applying  a 
weak  solution  of  inspissated  and  purified  ox-gall. 

Colour  of  the  Film.  This  exercises  a  great  effect  upon  the 
subsequent  operation  of  printing.  The  yellow-stained  film  is  the 
most  non-actinic  and  slowest,  the  olive-greenish  black  being  the 
quickest  and  giving  the  most  brilliant  prints. 

Combination  Printing.   See  Printing. 

Composition.  An  artistic  term  denoting  the  grouping  of  the 
materials  of  a  picture  so  as  to  form  a  pleasing  and  harmonious 
whole.  It  can  be  well  said  of  the  majority  of  photographs  taken 
by  amateurs  that  there  is  but  little  composition  in  them ;  most 
are  but  a  faithful  portrayal  of  subjects  as  they  are  found 
naturally.    But,  whilst  the  photographer  does  not  possess  that 

89 


Con] 


DICTIONARY  OF  PHOTOGRAPHY. 


power  of  composition  which  is  the  backbone  of  the  artist's  work, 
he  x:an  at  least  modify  to  some  extent  the  scenes,  etc.,  ready 
found  to  his  hand.  The  amateur  who  desires  rather  to  produce 
pictures  than  faithful  photographs  is  recommended  to  obtain 
Robinson's  "  Pictorial  Effect  in  Photography,"  and  "  Picture 
Making  by  Photography,"  in  which  the  subject  is  most  ably 
treated  at  great  length.  These  two  books  should  form  part  of 
the  library  of  every  one  practising  photography. 

Concave.  A  term  applied  to  lenses  when  the  surfaces  are 
hollowed  out  like  the  inside  curve  of  an  arch. 

Concave,  Concavo-Concave,  Concavo-Convex  Lens.  See 

Lens. 

Condensers.  These  are  combinations  of  lenses  of  various 
forms,  which  have  for  their  purpose  the  condensing  or  collecting 
of  rays  of  light  which  would  otherwise  be  scattered  or  lost.  They 
form  a  necessary  part  of  every  lantern,  and  take  various  forms. 
The  action  of  a  condenser  is  well  shown  in  the  following 
diagrams.    Let  R  be  the  light  emitting  rays  which  pass  through 


Fig.  12. 


the  negative  on  slide  p,  and  let  o  be  the  objective  or  projecting 
lens.  It  will  be  seen  from  this  that  practically  very  little  light 
passing  through  the  slide  reaches  the  objective ;  but  by  placing 
a  condenser  between  the  radiant  and  slide  it  will  be  seen  that  it 
refracts  light  which  would  otherwise  be  lost,  as  shown  by  the 
dotted  lines,  and  condenses  it,  so  that  it  is  utilised  by  the  pro- 
jecting lens.   Simple  lenses  could  be  used  for  condensers,  but  on 

90 


DICTIONARY  OF  PHOTOGRAPHY. 


[Con 


account  of  their  great  thickness  and  the  spherical  aberration  they 
would  be  liable  to  crack,  and  would  give  but  confused  images. 
It  has  been  the  custom,  therefore,  to  split  the  single  lenses,  and 
mount  the  two  lenses  with  their  convex  surfaces  nearly  touching, 


Fig.  13- 


as  in  fig.  14.  A  further  improvement,  suggested  by  Mr.  Traill 
Taylor,  was  the  form  shown  in  fig.  1 5,  which  consists  of  a  meniscus 
lens  and  a  double  convex,  preferably  a  crossed  lens.  It  is 
essential  with  a  lantern — very  essential — that  as  much  light  as 


Fig.  14.  Fig.  15. 


possible  should  be  utilised,  and  assuming  the  dotted  lines  a  and  b 
to  represent  an  angle  of  illumination  of  900,  it  is  seen  that 
unless  the  condenser  is  placed  very  close  to  the  light,  and  is 
of  short  focus,  it  cannot  grasp  more  than  c  d  ;  therefore,  by  placing 
a  small  lens  nearer  the  radiant,  as  in  fig.  16,  it  is  evident  that 

9i 


Con] 


DICTIONARY  OF  PHOTOGRAPHY. 


more  light  will  be  collected,  provided  the  third  lens  is  thin  and 
of  long  focus,  when  the  light  is  brought  to  within  two  inches 


Fig.  16. 


of  the  small  lens,  and,  passing  through  it,  diverges,  and  then  is 
rendered  parallel  by  the  second  lens  and  condensed  by  the  third 


Fig.  17. 

lens.  Further  than  that,  by  using  three  lenses  the  spherical 
aberration  is  reduced  to  one-ninth  of  that  of  a  single  lens. 


Fig.  18. 


Mr.  Traill  Taylor  suggested  many  years  ago  the  condenser  shown 
in  fig.  17,  which  consists  of  three  plano-convex  lenses,  the  centre 


92 


DICTIONARY  OF  PHOTOGRAPHY.  [Con 


being  achromatised.  This,  however,  is  expensive.  Grubb  sug- 
gested the  form  shown  in  fig.  18,  in  which  A  is  a  piece  of  plain 
glass  to  absorb  the  heat,  b  a  plano-convex  lens  which  acts  as  a 
condenser,  c  a  plano-convex,  and  d  an  over-corrected  combina- 
tion. From  c  to  D  the  rays  are  practically  parallel,  and  thence 
diverge,  and  are  condensed  by  the  large  lens  E.  The  best  form  of 
condenser,  when  only  two  lenses  are  used,  is  that|shown  in  fig.  19, 
according  to  Mr.  Traill  Taylor,  whose  notes  on  this  subject  I  have 


Fig.  19. 


condensed,  and  consists  ol  a  plano-convex  lens  with  its  flat  side 
to  the  radiant,  the  second  lens  being  a  crossed  lens.  Most  con- 
densers are  made  of  crown  glass,  and  have  a  slightly  greenish 
tinge.  Colourless  optical  flint  would  be  better,  but  the  price 
would  be  higher.  All  condensers  shouid  be  so  loosely  mounted 
in  thin  cells  that  they  can  be  turned  round,  otherwise  the  expan- 
sion by  the  heat  may  cause  them  to  crack.  Clock  glasses  filled 
with  liquid  have  been  suggested  as  condensers  for  enlarging,  but 
these  are  so  long  in  focus  as  to  be  practically  useless. 

Conjugate  Foci.   See  Focus. 

Contact,  Optical.  Any  two  substances  brought  into  mechanical 
union  one  with  the  other,  so  as  to  absolutely  join,  and  made  to 
present  but  two  instead  of  four  surfaces,  are  said  to  be  in  optical 
contact.  A  familiar  example  is  the  common  mirror,  where  the 
amalgam  and  glass  are  in  absolute  optical  contact. 

Contrast.  The  placing  of  the  light  and  shade  and  objects 
in  a  photograph  that  they  may  give  due  value  the  one  to  the 
other. 

Convex.  The  opposite  to  concave — i.e.,  shaped  on  the  exterior 
into  a  spherical  or  round  form. 

93 


Cop] 


DICTIONARY  OF  PHOTOGRAPHY. 


Copal  (Ger.,  Copalharz ;  Fr.,  Copal;  Ital.,  Gomma  copale). 
A  resinous  substance  obtained  from  certain  leguminous  trees, 
from  Madagascar,  China,  Africa,  and  America.  It  is  also  found 
as  a  fossil.  It  occurs  in  pale  yellowish  tears,  which  are  insoluble 
in  water,  slightly  soluble  in  alcohol,  more  so  in  alcohol  and 
camphor,  freely  soluble  in  chloroform,  ether,  and  turpentine.  It 
is  used  for  making  varnishes. 

Copper,  Bromide  of  (Ger.,  Kupferbromid ;  Fr.,  Bromure  de 
cuivre ;  Ital.,  Bromuro  di  rame).  CuBr2  =  223*3.  Synonym: 
Cupric  Bromide.  It  occurs  as  a  blackish  powder,  or  in  light-blue 
needle-like  crystals,  and  is  formed  by  dissolving  cupric  oxide  in 
hydrobromic  acid,  evaporating  and  crystallising,  and  by  mixing 
solutions  of  cupric  sulphate  and  bromide  of  potash,  evaporating, 
and  separating  the  sulphate  of  potash.  It  is  a  deliquescent 
salt,  and  slightly  soluble  in  alcohol.    It  is  used  as  an  intensifier. 

Copper,  Chloride  of  (Ger.,  Kupferchlorid ;  Fr.,  Chlorure  de 
cuivre;  Ital.,  Cloruro  di  rame).  CuCl2  =  134*3.  Synonym : 
Cupric  Chloride.  Formed  in  a  similar  manner  to  the  bromide, 
with  hydrochloric  acid,  or  by  mixing  a  solution  of  cupric  sulphate 
and  calcium  chloride,  filtering  from  the  precipitate  of  calcium 
sulphate,  evaporating,  and  drying.  It  forms  brilliant  emerald- 
green  needles,  which  are  very  deliquescent  and  easily  soluble  in 
alcohol.  It  is  used  as  a  reducer,  and  in  Obernetter's  copper 
process.  There  is  also  a  lower  chloride,  cuprous  chloride  CuCl 
or  Cu2Cl;,,  which  is  only  used  as  a  convenient  absorbent  of  chlorine 
in  the  preparation  of  chloroplatinite  of  potash. 

Copper,  Sulphate  of  (Ger.,  Kupfersulfat,  or  Kupfervitriol ; 
Fr.,  Sulfate  de  cuivre,  or  Vitriol  bleu ;  Ital.,  Sulfato  di  rame). 
CuS04,5H20=249'3.  Synonyms:  Cupric  Sulphate,  Blue  Cop- 
peras, Blue  Vitriol.  This  is  made  by  roasting  copper  pyrites  with 
free  access  of  air,  lixiviation  of  the  mass  with  water,  evaporating, 
and  crystallising.  It  occurs  in  beautiful  blue  crystals,  some  of 
very  large  size,  which  effloresce  on  exposure  to  air,  lose  all  their 
water  of  crystallisation,  and  form  a  white  powder,  which  is 
extremely  hygroscopic.  Cupric  sulphate  has  been  used  as  an 
addition  to  the  ferrous  oxalate  developer,  its  action  being 
stated  to  be  merely  a  retarding  of  oxidation  of  the  ferrous 
sulphate. 

94 


DICTIONARY  OF  PHOTOGRAPHY. 


[Cop 


Copying.  This  is  an  operation  which  is  frequently  necessary, 
and  may  be  divided  into  three  heads  for  convenience  :  (a)  copy- 
ing black-and-white  objects ;  (b)  copying  photographs ;  (c)  copy- 
ing coloured  objects,  like  oil-paintings,  missals,  etc. 

(a)  Copying  Black-a?id-White  Work,  such  as  Engravings, 
Line-Drawings,  etc.  For  the  professional  worker  wet  collodion 
undoubtedly  still  holds  its  own  in  this  branch ;  but  for  the 
amateur,  or  when  only  one  or  two  subjects  have  to  be  copied, 
dry  plates  may  be  used  with  perfect  results.    In  copying  a  black- 


Fif.  20. 

and-white object  we  want  no  gradation,  no  half-tones,  no  shadows; 
merely  black  and  white.  Should  the  paper  show  a  grain  it  is 
necessary  to  light  the  subject  in  such  a  manner  that  no  sign  of 
this  grain  is  visible,  which  can  usually  be  effected  by  a  full  front 
lighting,  and  by  even,  all-round  illumination  as  is  obtained  out  of 
doors.  Frequently  it  is  necessary  to  use  some  support  to  retain 
the  page  of  a  book  or  print  flat ;  this  support  may  be  either  a 
piece  of  stout  wood  placed  behind  the  leaf  or  print,  which  can 
then  be  held  in  position  by  a  couple  of  stout  india-rubber  rings, 
if  the  print  to  be  copied  cannot  be  pinned  flat  by  the  aid  of 

95 


Cop] 


DICTIONARY  OF  PHOTOGRAPHY. 


drawing-pins.  A  capital  copying-stand,  suggested  by  the  "  Ker- 
nel," the  author  of  "  Photography  in  a  Nutshell,"  is  shown  in 
fig.  20.  This  is  so  obvious  that  we  need  hardly  explain  its 
action.  The  most  suitable  plates  are  those  commercial  brands, 
which  are  specially  made  for  this  work,  and  which  are  called 
'*  photo-mechanical "  ;  but,  failing  these,  any  ordinary  slow  lantern 
plate  designed  for  giving  black  tones  can  be  used.  The  lens 
should  be  a  rapid  rectilinear  or  doublet  of  not  too  long  a  focus, 
because  it  must  be  remembered  that  when  copying  at  close 
quarters  the  focus  is  lengthened,  and  therefore  a  lens  of  such  a 
focus  must  be  chosen  that  the  increased  focus  is  not  too  long  for 
the  bellows  of  the  camera.  This  increase  in  focus  must  be  taken 
into  account  when  estimating  the  factor  of  stop  aperture  for  cal- 
culating exposure.  The  exposure  of  course  will  vary  enormously 
with  the  subject ;  but,  as  some  guide,  I  may  say  that  copying  a 
black-and-white  line-drawing,  such  as  one  of  the  diagrams  in 
this  book,  the  same  size,  using  // '22  diaphragm  and  a  photo- 
mechanical plate  at  noon  in  an  ordinary  room,  facing  a  north- 
light  window  on  a  bright,  but  not  sunny  day,  the  exposure  given 
was  40  sees.,  and  found  to  be  correct.  For  development  ferrous 
oxalate,  eikonogen,  amidol,  and  metol  are  useless,  and  the  best 
results  will  be  obtained  by  using  either  hydroquinone  or  pyro ; 
glycin  also  being  of  value,  though  for  this  work  I  have  not 
obtained  such  successful  results  as  with  pyro.  Reference  to  the 
Appendix  will  give  the  formulae  of  the  different  makers,  that  of 
Mawson  and  Swan's  being  the  one  I  have  succeeded  best  with. 
The  main  point  in  developing  is  to  obtain  clear  glass  in  the  lines 
representing  the  blacks  of  the  print ;  density  of  the  part  represent- 
ing the  paper  is  of  secondary  consideration  because  it  may  be 
obtained  afterwards  by  intensification,  though  with  correct  ex- 
posure good  density  combined  with  clear  glass  can  be  easily 
obtained.  Continue  development  as  far  and  as  long  as  possible, 
but  on  the  slightest  sign  of  any  deposit  on  the  lines  instantly 
drop  the  plate  in  an  acid  fixing-bath.  After  fixation  wash 
thoroughly,  and  then  examine  the  negative ;  should  there  be 
any  deposit  in  the  lines  reduce  by  the  aid  of  Belitzski's  reducer, 
thoroughly  wash,  soak  for  10  mins.  in  a  hypo  eliminator,  again 
wash,  and  intensify  with  the  potassio-silver  cyanide  intensifier. 

{b)  Copying  Photographs.  In  copying  photographs,  photo- 
gravures, collotypes,  or  any  prints  in  which  there  is  half-tone,  it 

96 


DICTIONARY  OF  PHOTOGRAPHY.  [Cry 

is  advisable  to  use  a  medium  rapidity  or  ordinary  plate,  and  with 
prints  with  a  considerable  amount  of  heavy  shadow  it  is  advisable 
even  to  use  a  more  rapid  plate.  The  developer  should  be  the 
one  usually  recommended  for  the  plates,  or  that  which  the 
operator  is  in  the  habit  of  using,  and  soft,  full-of-detail  negatives 
should  be  aimed  at. 

(c)  Copying  Coloured  Objects,  Oil-Painti?igs,  etc.  With  all 
coloured  objects  there  is  only  one  particular  kind  to  use,  and 
that  is  the  colour-sensitive  plate.  When  the  object  contains 
much  red,  then  one  sensitised  for  this  colour  must  be  used  ■  if 
there  is  much  blue  or  violet,  then  must  also  a  yellow  screen  or 
filter  be  employed.  In  fact,  it  may  be  taken  for  granted  that 
with  all  oil-paintings  a  yellow  screen  is  advisable,  as  it  prevents 
the  reflections  from  the  cracks  and  inequalities  of  the  surface. 
The  best  light  in  which  to  copy  all  coloured  objects  is  sunlight  : 
the  colours  are  more  correctly  rendered.  Next  to  sunlight  would, 
of  course,  come  the  electric  light,  and  then  magnesium  ribbon.' 
In  copying  oil-paintings  the  question  of  lighting  is  an  important 
one,  as  the  thicknesses  of  the  coats  of  paint  will  show  with 
strong  light  from  one  particular  direction  ;  at  the  same  time,  it 
must  be  borne  in  mind  that  artists  frequently  desire  to  see  these 
inequalities  or  brush  marks,  whilst  for  ordinary  purposes  the 
brush  marks  are  objectionable.  For  the  correct  reproduction  of 
colours  it  is  necessary  to  use  light  filters,  which  will  cut  off  the 
action  of  the  blue  and  violet  rays,  whilst  the  red  and  yellow  act. 
The  composition  of  these  screens  for  this  purpose  is  given  under 
Heliochromy  (q.v.).  Further  information  will  also  be  found 
under  Screens  and  Isochromatic  Photography. 

Crystal  Varnish.    This  is  specially  designed  for  varnishing 
lantern-slides  and  transparencies,  and  is  made  by  dissolving- 
Gum  dammar    ...       ...      25  grs. 

in 

Benzole        ...       ...       ...       ...  1  oz. 

another  formula  being 

Canada  balsam       ...       ...    5  parts 

Shellac  (yellow)    !6o 


Sandarac 
Alcohol 


  170  , 

  1000  , 

97  h 


Cur] 


DICTIONARY  OF  PHOTOGRAPHY. 


rr 


Fig.  22. 


photographer,  be  formed  on  a  plane  or  flat  surface ;  but,  taking 
a  single  lens  (fig.  21),  we  shall  find  that  the  focus  for  b  is  at  e, 
whilst  the  focus  for  a  is  at  g,  for  c  at  f,    h  i  represents  the 

98 


DICTIONARY  OF  PHOTOGRAPHY. 


[Cya 


plane  ot  the  sensitive  plate,  from  which  it  is  obvious  that, 
theoretically,  only  the  point  e  would  be  in  focus.  A  concave  or 
negative  lens  has,  as  is  well  known  (see  also  Chromatic 
Aberration),  no  real  focus,  and  the  marginal  rays  are  more 
refracted  than  the  central,  so  that  by  combining  a  concave 
with  a  convex  lens  we  lengthen  the  focus  of  the  marginal 
rays,  and  thus  flatten  the  field.  The  use  of  a  stop  also  still 
further  increases  the  flatness  of  field,  as  shown  in  fig.  22. 
a  b  c  is  a  plane  object,  and  /  a  lens  ;  the  rays  from  b — the 
point  situated  on  the  axis — will  come  to  a  focus  at  F  ;  but,  the 
rays  from  «,  (1.,  II.,  III.,  iv.,  v.)  are  refracted  to  a,  b,  c,  d,  e,  and 
from  c  (l,  2,  3,  4,  5  )  are  refracted  to  a',  b',  c\  d',  e' .  From  this 
figure  it  is  evident  that  only  a  iv.,  a  v.,  c  5  and  c  4  have  their 
focus  anywhere  near  F,  so  that  by  placing  a  diaphragm,  Op, 
so  as  to  intercept  all  but  these  rays  we  shall  practically  have 
a  flat  field. 

Cutting  Prints.  This  is  trimming  off  the  unnecessary  part 
of  the  print  till  of  the  desired  size.  It  should  always  be  done 
prior  to  toning,  to  save  the  waste  of  gold  in  toning  unnecessary 
matter.  It  should  always  be  done  whilst  the  print  is  dry. 
Plate-glass  cut,  with  polished  edges,  to  certain  sizes  can  be 
obtained  commercially,  but  any  old  negative  glass  or  flat  ruler 
will  do.  Numerous  shaped  knives  are  sold  for  this  purpose 
but  the  author  has  found  a  leather-cutter's  knife,  termed  a 
dicker's  knife,  the  most  convenient,  and  the  price  is  but  a 
few  pence.  Too  many  amateurs  consider  that  the  finished 
print  should  be  exactly  the  full  size,  when  much  more  pleasing 
pictures  can  be  produced  by  trimming  off  certain  portions  of  the 
print. 

Cyanine  (Ger„  Cyanin,  or  Chinolinbleu;  Fr.,  Cyanine,  or 
Bleude  quinoleine ;  Ital.,  Cianind).  Synonyms:  Cyanine,  Cyanin 
Iodide,  Quinolin,  or  Chinolin  Blue.  C.^I-^NJ  =  525.  This  is 
prepared  by  the  action  of  iodide  of  amyl  on  quinolin  ;  it  occurs 
as  a  dark  blue  powder  or  prismatic  crystal,  with  metallic  lustre; 
it  is  not  very  soluble  in  water,  but  more  so  in  alcohol.  As 
cyanine  is  sensitive  to  light  it  must  be  kept  in  the  dark.  It  is 
one  of  the  best  sensitisers  for  red,  and  for  this  purpose  is  used 
in  orthochromatic  work,  the  disadvantage  being  that  the  plates 
are  very  liable  to  fog,  and  therefore  Dr.  Eder  suggests  the  use  of 

99 


Cya] 


DICTIONARY  OF  PHOTOGRAPHY. 


chloro-cyanin,  which  has  not  this  action,  and  gives  the  following 
directions  for  making  the  same  : — Powder  the  ordinary  com- 
mercial iodo-cyanin';  place  in  a  porcelain  or  platinum  dish,  and 
cover  with  some  water  and  hydrochloric  acid ;  evaporate  to 
dryness  with  constant  stirring ;  the  mass  thus  obtained  is  again 
wetted  with  hydrochloric  acid,  and  again  evaporated,  when 
hydriodic  acid  is  given  off  and  chloro-cyanin  is  left  behind.  By 
weighing  the  capsule  containing  the  cyanin  before  and  after  this 
treatment  one  may  dissolve  the  mass  at  once  in  ale  ihol  and  keep 
in  the  dark  for  use. 

Cyanotype.  Synonyms:  Negative  Cyanotype,  Ferroprussiate, 
or  Blue  Process.  A  process  discovered  in  1842  by  Sir  John 
Herschel.  It  is  called  negative  cyanotype,  because  it  produces 
copies  of  engineers'  or  architects'  plans  with  white  lines  on  a  blue 
ground,  the  action  being  the  reduction  of  a  ferric  salt  by  light 
to  the  ferrous  state,  and  the  precipitation  of  Prussian  blue  by 
the  action  of  ferridcyanide  of  potassium.  Herschel's  formula 
was 

A. 

Potassium  ferridcyanide    8  parts. 

Water    50  ,, 

B. 

Ammonio-citrate  of  iron    ...       ...       ...      10  parts. 

Water    50  „ 

The  solutions  are  mixed  in  equal  parts,  filtered,  and  kept  in  the 
dark,  and  'will- keep'jfor  some  little  time.  The  ferridcyanide 
should  (be  just  rinsed  [with  water  to  clean  it  from  any  adherent 
powder,Tand  the  solution  should  be  of  a  yellowish  or  orange-red 
colour,  and'not  greenish  blue ;  if  the  latter  colour,  it  should  be 
thrown  away  and  fresh  mixed  up,  or  heated  and  a  few  drops  of 
bromine  water  added.  Latimer  Clark  suggested  the  following 
improved  formula : — 

A. 

Ammonio-citrate  of  iron    90  parts. 

Water    ,  3°°  •> 

100 


DICTIONARY  OF  PHOTOGRAPHY. 


B. 

Potassium  ferridcyanide    ...       ...       ...  80  parts. 

Liquor  Ammonia    ...       ...       ...       ...  7  „ 

Water    300  ,, 

Sat.  Sol. oxalic  acid  ...       ...       ...       ...  60  ,, 


This  is  more  sensitive.    Ehrmann  and  Fries   suggested  the 

addition  of  bichromate  of  potash,  the  former  stating  that  this 

addition  kept  the  papers  unchanged  for  from  three  to  five 

months.  Ehrmann's  formula  is 


A. 

Ammouio-citrate  of  iron     ...       ...       ...     60  parts. 

Water   256  „ 


B. 

Potassium  ferridcyanide    ...       ...       ...      40  parts. 

Water   256 

Mix  in  equal  parts,  and  to  every  960  parts  of  the  mixture  add  1 
part  of  bichromate  of  potash.  Watt  suggested  the  addition  of 
boric  acid  for  the  same  purpose. 

A. 

Ammonio-citrate  of  iron    ...  ...  ...  96  parts. 

Boric  acid     ...       ...       ...  ...  ...  1  part. 

Water         ...       ...       ...  ...  ...  190  parts. 


B. 

Potassium  ferridcyanide    ...       ...       ...      96  parts. 

Water    196  „ 

Mix  in  equal  parts.  Rockvvood  suggested  the  addition  of  gum 
Arabic,  or  dextrin,  as  a  preventative  of  the  solution  sinking  into 
the  paper. 

A. 

Potassium  ferridcyanide    ...       ...       ...       1  pait. 

Water    10  parts. 

j  01 


Cya] 


DICTIONARY  OF  PHOTOGRAPHY. 


B. 

Ammonio-citrate  of  iron    ...       ...       ...  3  parts. 

Water     10  „ 

Gum  Arabic,  or  dextrin    \  part. 

The  sensitising  solution  is  spread  over  well-sized  paper  with  a 
pad  or  brush,  working  in  one  direction,  and  then  across  to 
even  the  marks  out.  The  paper  is  then  hung  up  to  dry,  and 
appears  of  a  greenish-yellow  colour ;  and  where  the  light  acts 
on  it  it  turns  blue.  After  exposure  it  is  merely  washed  in 
water,  when  the  image  becomes  bright  blue,  and  the  ground,  or 
unexposed  portion,  should  remain  quite  white.  Over-printed 
proofs  may  be  reduced,  after  thoroughly  washing,  by  being 
dipped  into  a  weak  solution  of  ammonia  or  a  2  per  cent,  solution 
of  sodium  carbonate,  well  washing,  and  then  dipping  into  weak 
hydrochloric  or  acetic  acid  and  well  washing.  Under-printed 
proofs  may  be  intensified  by  immersion  in  a  solution  of  ferric 
chloride,  or  nitrate  or  sulphate  of  iron,  3*5  parts  to  1000  parts  of 
water,  till  the  image  appears  darker  in  colour,  and  then  well 
washing.  Corrections,  or  taking  out  spots,  etc.,  can  be  effected 
by  touching  the  dry  prints  with  a  4  per  cent,  solution  of  oxalate 
of  potash,  with  which  also  titles  may  be  written ;  and  if  red 
aniline  ink  be  added  to  the  above,  or  4  parts  of  oxalate  be 
dissolved  in  100  parts  of  the  red  ink,  the  title  will  appear  red  on 
the  blue  ground.  The  blue  images  thus  obtained  can  be  con- 
verted into  ink  images,  or  blackish  images,  by  soaking  first  in 
5  per  cent,  carbonate  of  potash  solution,  washing,  and  then 
immersing  in  a  similar  strength  of  tannin  solution ;  a  good 
brownish-black  colour  is  obtained  by  immersing  them  direct 
in  a  saturated  solution  of  carbonate  of  soda,  mixed  with  an 
equal  quantity  of  water,  to  which  has  been  added  as  much 
tannin  as  it  will  dissolve.  It  has  also  been  suggested  immersing 
the  prints  in  weak  hydrochloric  acid  to  clear  the  whites,  then  in 
weak  ammonia  1  :  15,000,  and  finally  in  a  bath  of 

Alum  ...       ...       ...       ...       ...       ...      10  parts. 

Tannin         ...       ...       ...       ...       ...       1  part. 

Water    130  parts. 

exposing  the  prints  to  sunshine  for  ten  minutes,  and  then  bathing 
in  dilute  ammonia.     Cyanotype,  or  Ferroprussiate  prints,  may 

102 


DICTIONARY  OF  PHOTOGRAPHY. 


[Cya 


also  be  converted  into  silver  prints  by  immersing  the  prints  in 
a  2  per  cent,  solution  of  silver  nitrate,  washing  well,  and  de- 
veloping the  pale  yellow  image  with  ferrous  oxalate  developer. 
Instead  of  using  a  mixture  of  ferridcyanide  and  ammonio-citrate 
as  the  sensitive  mixture,  the  latter  solution  alone  may  be  used 
for  sensitising  the  paper,  and  the  ferridcyanide  solution  used  as 
a  developer. 

Positive  Cyanotype,  or  Pellet's  Process.  This  process  is  the 
opposite  to  the  last — that  is,  it  gives  blue  lines  on  a  white  ground 
from  a  plan,  or,  in  other  words,  where  the  light  acts  no  image  is 
formed ;  only  on  those  parts  where  the  light  does  not  act  is  a 
precipitate  of  Berlin  blue  formed  by  the  action  of  the  ferro- 
cyanide  of  potassium  with  a  ferrous  salt.  This  process  was  also 
suggested  by  Herschel,  but  no  satisfactory  progress  was  made 
till  Pellet  patented  in  1877  his  process  of  adding  a  viscous 
substance  to  the  sensitising  liquid.    Pellet  used 

Oxalic  acid   5  parts. 

Ferric  chloride        ...       ...       ...       ...      10  ,, 

Water    100  ,, 

Gum  Arabic...       ...       ...       ...       ...  9-5  ,, 

In  1880  Collache  patented  a  similar  process,  and  used 

Gum  Arabic   ...    7-10  parts. 

Citric  acid  ...       ...       ...       ...     2-3  ,, 

Ferric  chloride  solution  45°B.       ...       ...     4-6  ,, 


Pizzighelli  in  1881  gave  good  working  formula:  for  this  pro- 


Water 


...  81-87 


cess  : — 


1. 


Gum  Arabic  . . . 
Water 


20  parts. 
100  ,, 


II. 


Ammonio-citrate  of  iron 
Water   


50  parts. 
100 


111. 


Ferric  chloride 
Water 


50  parts. 
100 


Cya] 


DICTIONARY  OF  PHOTOGRAPHY. 


The  two  latter  solutions  will  keep  several  weeks.  The  solutions 
are  mixed  in  the  following  proportions  and  order  : — 

Solution  No.  I.    ,   ...     20  parts. 

No.  II   ...       8  „ 

No.  Ill   5  „ 

As  soon  as  mixed  this  solution  is  thin,  then  becomes  thick  and 
cloudy,  and  then  clear  and  liquid  again,  when  it  is  ready  for  use. 
Well-sized  paper  is  evenly  coated  with  this  solution  with  a  broad 
brush,  and  the  coating  evened  out  with  another  brush.  It  must 
be  quickly  dried  in  a  warm  room,  and  protected  from  damp  and 
light.  In  printing,  the  image  appears  as  yellow  on  a  darker 
ground.    The  developer  is 

Potassium  ferrocyanide    20  parts. 

Water    100  ,, 

which  should  be  spread  over  the  proof  with  a  broad  brush,  care 
being  taken  that  no  solution  touches  the  back  of  the  paper  or 
stains  will  be  produced.  As  soon  as  the  image  appears  of  a 
deep  blue  colour,  the  print  should  be  well  washed,  and  then  laid 
in  dilute  hydrochloric  acid  1  :  10  till  the  ground  appears  white  ; 
and  the  print  should  then  be  well  washed  and  dried.  Waterhouse 
has  suggested  another  process. 

I 

Gum  Arabic  170  parts. 

Water   650  ,, 

II. 

Tartaric  Acid    ...     40  parts. 

Water      150 

III. 

Sol.  ferric  chloride  45  0  B   1 50-1 20  parts. 

Mix  solutions  1  and  2,  and  add  gradually,  with  constant 
stirring,  No.  3  ;  allow  the  mixture  to  stand  for  twenty-four  hours, 
and  then  dilute  with  water  till  the  specific  gravity  is  rioo.  The 
solution,  and  the  paper  sensitised  with  it,  will  keep  for  some 
considerable  time.  The  exposure  in  direct  sunlight  is  from  15 
to  40  seconds,  in  diffused  light  from  10  to  30  minutes.    As  the 

104 


DICTIONARY  OF  PHOTOGRAPHY.  [Dag 

image  formed  by  light  is  only  very  faintly  visible,  it  is  advisable 
to  use  a  strip  of  paper,  either  exposed  under  one  corner  of  the 
plan  or  drawing,  or  under  a  similar  and  smaller  one  at  the 
same  time ;  and  when  test  slips  from  this  develop  a  blue  image 
on  a  yellow  ground  the  exposure  is  sufficient.  The  developer  is  a 
20  per  cent,  solution  of  ferridcyanide  of  potassium.  The  edges  of 
the  print  are  turned  back  so  as  to  form  a  sort  of  dish,  or  protecting 
shield,  so  that  no  developer  gets  on  the  back  of  the  paper.  The 
print  is  then  carefully  floated  on  to  the  developer  and  left  for 
about  thirty  minutes,  and  then  examined  at  one  corner  till  blue 
spots  begin  to  appear,  when  the  print  should  be  immediately 
removed,  floated  carefully  again  on  a  dish  of  clean  water  and  left 
for  some  minutes,  and  then  immersed  in  dilute  hydrochloric 
acid  1  :  100,  and  any  blue  spots  removed  by  carefully  brushing  ; 
and,  finally,  the  print  should  be  laid  at  the  bottom  of  an  empty 
dish  and  a  vigorous  stream  of  water  from  a  rose  or  tap  allowed 
to  play  on  it.  Corrections  are  made  by  the  same  solution 
previously  mentioned,  the  spots  being  touched  with  a  fine  pencil 
and  blotted  off  with  clean  blotting-paper. 

Daguerreotype.  The  oldest  process  for  obtaining  any  per- 
manent picture ;  discovered  by  Daguerre.  A  sensitive  surface 
of  silver  iodide  and  bromide  was  formed  by  exposing  a  silvered 
copper  plate  to  the  direct  action  of  the  metalloids.  After  ex- 
posure, which  was  inordinately  prolonged,  the  development  was 
effected  by  exposing  the  plate  to  the  vapour  of  metallic  mercuryi 
which  was  deposited  on  the  plate  as  an  amalgam  of  silver  and 
mercury.  The  unacted-upon  iodide  and  bromide  were  then 
dissolved  by  cyanide  of  potassium  or  hyposulphite  of  soda,  and 
the  image  toned  by  sel  d'or.    (See  Gold  Hyposulphite.) 

Daguerreotype,  To  Clean  and  Copy.  Carefully  remove  the 
daguerreotype  from  its  frame  and  separate  from  its  covering 
glass,  and  place  face  upwards  in  a  dish  of  cold  water.  Be 
extremely  careful  not  to  touch  the  front  of  the  plate,  as  the 
slightest  touch  will  leave  a  permanent  mark.  Lift  the  plate  by 
the  corners,  and  remove  the  paper  from  the  back  when  suffi- 
ciently soaked ;  rinse  the  plate  thoroughly,  and,  should  the  water 
be  repelled  as  though  the  plate  were  greasy,  flow  over  a  little 
methylated  spirit.  If  the  tarnish  on  the  edges  be  blue  in  colour, 
immersion  in  an  ordinary  fixing  bath  will  remove  the  same ;  but 

io5 


Dal] 


DICTIONARY  OF  PHOTOGRAPHY. 


if  any  bronzing  is  visible,  make  a  solution  of  cyanide  of  potas- 
sium, ten  grains  to  the  ounce,  and  keep  pouring  this  on  and  off 
till  all  tarnish  is  removed.  Wash  the  plate  thoroughly  to  free 
from  cyanide,  and  rinse  well  with  distilled  water ;  then  take  hold 
of  one  corner  of  the  plate  with  a  pair  of  pliers,  and  dry  evenly 
from  a  top  corner  downwards  over  a  spirit  lamp  or  Bunsen 
burner.  If  any  stain  or  deposit  is  left  by  unequal  drying,  the 
plate  must  again  be  rinsed  with  distilled  water,  and  dried  in  the 
same  way.  The  chief  point  is  not  to  touch  the  plate  with  any- 
thing but  the  liquids,'  or  a  mark  will  be  made  which  nothing 
will  eradicate.  To  copy  a  daguerreotype  the  best  plan  will 
be  to  place  it  inside  a  deep  box,  lined  with  velvet  or  black 
cloth,  with  a  hole  in  the  lid  for  the  lens  to  peep  through,  and  a 
piece  cut  out  of  one  side  only  to  illuminate  the  plate  by — 
sunshine  is  best,  though  the  light  from  an  enlarging  lantern 
is  equally  as  effective.  In  most  daguerreotypes  the  marks  of 
the  buffer  are  seen  as  fine  horizontal  lines.  In  copying,  these 
should  be  placed  vertical,  and  when  in  that  position  are  barely 
visible. 

Dallastint.  A  secret  process  of  photo-mechanical  printing, 
famous  for  its  rendering  of  half-tone. 

Dammar.  A  tasteless,  odourless,  whitish  resin  obtained  from 
the  Amboyna  pine,  whose  habitat  is  the  Malay  Archipelago.  It  is 
used  in  varnish-making,  for  which  purpose  it  is  usually  dissolved 
in  turpentine,  or  benzole. 

Dark-Room.  The  room  in  which  all  operations  requiring 
actual  handling  of  the  sensitive  plate  must  be  conducted  It  is 
usually  lighted  by  daylight  filtered  through  some  non-actinic 
glass  or  medium.  It  was  the  custom  but  a  year  or  two  back 
to  utilise  none  but  the  deep  ruby  glass  for  this  purpose,  but 
now  some  equally  non-actinic  colours  giving  much  more  general 
illumination  are  used.  A  good,  safe  light  can  be  obtained  by 
using  what  is  termed  cathedral  green  glass,  with  one  thickness 
of  canary  medium.  The  author  invariably  uses  artificial  light 
from  a  paraffin  lamp,  as  by  this  light,  which  is  constant,  a  much 
better  idea  of  the  progress  of  development  can  be  obtained  than 
by  such  a  variable  quantity  as  daylight.  Whatever  light  is  used 
it  should  always  be  tested  by  placing  a  sensitive  plate  upon  the 
developing  table  with  some  opaque  substance,  such  as  a  piece 

106 


DICTIONARY  OF  PHOTOGRAPHY, 


[Den 


of  black  cardboard,  upon  it,  and  left  for  three  or  four  minutes 
and  then  the  plate  carefully  developed  should  show  no  image  of 
the  card.  The  general  arrangements  of  the  dark-room  must  be 
left  entirely  to  the  amateur,  but  the  following  may  be  considered 
to  be  some  of  the  principal  features  : — A  shelf  or  table  on  which 
to  develop.  This  should  be  of  a  convenient  height,  to  allow 
the  operator  to  sit  at  his  ease  whilst  developing.  It  should 
be  covered  with  some  non-absorbent  material,  such  as  sheet 
lead  or  zinc,  and  the  edge  of  this  should  be  turned  up  about 
a  quarter  of  an  inch  to  prevent  any  solution  which  might  be 
spilt  from  running  over.  There  should  also  be  a  sink,  with  a 
tap  and  a  good  supply  of  water.  Shelves  should  be  placed  at 
convenient  heights  for  th£  storing  of  bottles,  printing  frames, 
boxes,  etc.  The  room  and  developing  table  should  be  kept 
scrupulously  clean,  and  after  operations  all  solutions  spilt  and 
the  trays,  measures,  etc.,  should  be  cleaned  and  put  away. 

Dark-Tent.  A  portable  dark-room,  little  used  now,  but  ot 
absolutely  necessity  in  the  old  days  of  the  wet  process. 

Decomposition  of  Light.  White  light  on  passing  through 
a  prism  is  decomposed  or  separated  into  its  constituent  rays. 
All  lenses  being  formed  on  the  principle  of  a  prism,  it  is  evident 
that  light  passing  through  a  lens  would  be  decomposed  and  give 
rise  to  chromatic  aberration,  but  this  is  obviated  by  combining  a 
lens  of  different  shape  and  glass,  so  as  to  recombine  the  scattered 
rays.    (See  Spectrum  and  Lens.) 

Definition  is  the  accurate  concentration  by  the  lens  of  the 
light  from  a  point  in  an  object  to  the  corresponding  point  in  its 
image  without  spreading  to  adjacent  parts.  Perfection  of  defini- 
tion depends  chiefly  on  the  rapidity  of  the  lens,  on  the  com- 
position of  the  glass  employed,  the  relative  positions  and  forms 
of  the  surfaces  and  their  proper  grinding,  the  centreing  of  the 
elements  of  a  combination,  and,  in  a  doublet,  the  centreing  and 
due  separation  of  the  combinations. 

Deflection.  An  optical  term  used  to  denote  the  swerving 
from  its  straight  course  of  a  ray  of  light  when  passing  very  near 
an  opaque  object,  the  ray  being  deflected  towards  that  body. 

Density — literally  opacity  ;  and  in  this  sense  correct  density 
is  an  attribute  of  a  good  negative.    It  should  be  just  sufficient  to 

107 


Dep]  DICTIONARY  OF  PHOTOGRAPHY. 

give  due  relation  to  the  shadows,  and  yet  allow  the  detail  in 
the  high-lights  to  print.  Almost  all  plates  differ  in  the  value  of 
the  deposit  of  metallic  silver,  of  which  density  or  opacity  is 
formed ;  and  the  correctness  of  the  judgment  necessary  in  this 
particular  is  one  of  the  best  tests  of  a  good  worker — it  can  only 
be  obtained  by  experiment  with  every  brand  of  plate  used.  With 
some  the  development  must  be  pushed  till  the  high-lights  just 
show  on  the  back  of  the  film,  and  the  whole  surface  of  the 
plate  is  becoming  blackened  ;  whilst  with  others,  especially  those 
containing  iodide  or  those  having  a  film  rich  in  silver,  the  test 
of  the  blackening  of  the  surface  of  the  plate  will  usually  be 
sufficient.  The  colour  of  the  deposit  of  silver  affects  the  result 
in  a  great  measure.  If,  when  the  negative  has  been  fixed,  the 
amateur  finds  that  his  judgment  has  not  been  correct,  he  has, 
fortunately,  methods  of  increasing  or  decreasing  the  density,  as 
described  in  the  operations  of  Intensification  and  Reduction  (q.v.). 

Depth  of  Focus.   See  Focus. 

Detail.  The  definition  of  each  minute  part  or  parts  of  the 
material  of  a  picture,  whether  in  the  negative  or  print  therefrom. 

Detective  Or  Hand  Cameras.  These  are  cameras  of  par- 
ticular designs,  so  constructed  as  to  be  portable  and  unlikely  to 
attract  attention.  Their  name  is  legion  ;  their  makes  diversity 
itself ;  and  to  attempt  to  include  even  a  brief  description  of  them 
would  be  beyond  the  limits  of  space  at  my  command.  Practi- 
cally, however,  hand  cameras  may  be  divided  into  two  main 
classes:  (a)  those  with  automatic  plate  or  film-changing  appa- 
ratus ;  (b)  those  with  dark  slides.  I  do  not  intend  to  attempt  in 
any  way  to  describe  these.  Each  operator  must  decide  for  him- 
self which  pattern  meets  most  nearly  his  requirements  ;  but  we 
can  consider  the  individual  parts  of  the  camera. 

The  Lens.  As  one  of  the  chief  features  of  detective  work  is 
the  portrayal  of  objects  situated  at  varying  distances  from  the 
camera,  it  is  obvious  that  lenses  with  great  depth  of  Focus  {q.v.) 
are  required;  and  as  this  property  decreases  with  increase  of 
focal  length  and  aperture,  we  are  limited  in  our  choice  to  certain 
forms  and  apertures  of  lenses,  although  the  great  advance  made 
lately  in  practical  photographic  optics  has  given  us  instruments 
which  are  of  valuable  assistance  in  this  work.     It  will  be  found 

108 


DICTIONARY  OF  PHOTOGRAPHY. 


[Det 


that,  generally,  lenses  of  short  focus — i.e.,  which  have  a  focus  about 
equal  to  the  longer  base  of  the  plate  which  they  are  intended  to 
cover,  thus  for  a  quarter-plate  a  4-in.,  4o-in.,  or  5-in.  focus  lens 
— should  be  used.  The  rectilinear,  or  doublet  form  of  lens,  will 
be  found  the  best,  though  single  or  landscape  lenses,  working 
at  a  large  aperture,  fjZ  or  f/10,  will  often  serve  equally  as  well. 

The  Diaphragms  or  Stops.  The  question  of  aperture  is 
governed  by  two  considerations — the  first,  that  of  depth  of  focus  ; 
and  the  second,  the  actinic  power  of  the  light.  As  the  first 
increases  with  diminution  of  aperture,  the  smaller  the  diaphragm 
the  greater  the  depth  of  focus  ;  but  as  this  is  also  governed  by 
the  second  consideration,  it  is  obvious  that,  except  for  brightly  lit 
scenes,  such  as  seascapes  and  river  views,  and  work  on  the  sea- 
shore in  brilliant  sunshine,  it  would  be  injudicious  to  use  too  small 
an  aperture,  as  loss  of  detail  in  the  heavy  shadows  would  result- 
For  ordinary  work  //8  or  f\\o  will  be  found  quite  small  enough, 
while  for  sea  and  river  views  //16  will  be  found  large  enough. 
The  form  of  diaphragm,  whether  Iris  or  Waterhouse,  is  not  a 
vital  question,  as,  unless  the  former  is  controlled  from  the  out- 
side of  the  case,  there  is  no  advantage  in  its  use. 

The  Shutter.  This  should  be  capable  of  accurate  adjustment 
for  various  speeds,  from  very  rapid  to  slow.  From  j^th  to 
T^  sec.  will  be  found  quite  range  enough.  The  speed  at  which 
the  shutter  will  be  required  to  work  is  governed,  of  course,  by 
the  rapidity  of  movement  and  nearness  of  moving  object  to  the 
camera.  Reference  must  be  made  to  the  tables  and  rules  given 
under  Instantaneous  Photography,  p.  246,  for  information  upon 
this  point ;  but  as  it  would  be  impossible  to  make  any  calculation 
at  the  time  of  exposure,  the  operator  must  depend  upon  experi- 
ence alone  to  teach  him  all  that  is  required  on  this  point,  although 
the  application  of  these  rules  in  the  formation  of  a  set  table  of 
distances,  rapidity  of  movement,  and  speed  of  shutter,  would  be 
useful.  For  example,  supposing  a  4-in.  focus  lens  is  used,  by 
a  little  calculation  we  shall  find  that  a  shutter  must  work  at 
the  x^th  of  a  second  to  take  a  man,  walking  at  the  rate  of  four 
miles  an  hour,  twenty  yards  off;  and  a  horse  at  thirty  yards' 
distance,  going  about  twelve  miles  an  hour,  will  require  about 
/  th  of  a  second  speed. 

Plate  Arrangement  For  those  who  use  films,  roller  slides,  of 
course,  will  be  required  ;  but  for  the  general  run  the  question  as 

109 


Det] 


DICTIONARY  OF  PHOTOGRAPHY. 


to  which  is  the  better,  dark  slides  or  automatic  changing  methods, 
will  be  an  all-important  one. 

Focussing.  In  many  hand  cameras  this  is  altogether  dis- 
pensed with,  the  use  of  a  so-called  fixed-focus  lens  obviating 
the  necessity  of  the  same  ;  but  this  we  again  object  to  on  the 
same  principle  as  the  automatic  changing  arrangement  is 
objected  to — namely,  the  limitation  of  the  use  of  the  camera. 
The  table-  of  distances  beyond  which  everything  is  in  focus 
(p.  193)  will  be  useful  on  this  point,  and  the  question  of  fixed- 
focus  Lenses  (q.v.)  will  be  treated  of  separately. 

Finders.  Many  very  successful  workers  in  this  branch  of 
our  art  utterly  pooh-pooh  the  necessity  of  finders  ;  but,  speaking 
from  personal  experience,  these  are  an  absolute  necessity; 
nothing  is  more  annoying  than  to  find  on  development  that 
only  the  half  of  a  desired  object  is  included  on  the  plate. 
There  is,  however,  one  evil  which  is  usually  seen  with  most 
finders  of  the  camera  obscura  model,  the  one  usually  employed, 
and  that  is,  if  the  ground  glass  is  not  deeply  sunk  in  the  camera 
case,  any  bright  light  shining  on  the  same  effectually  prevents 
the  miniature  image  from  being  seen.  This  should  be  noted  in 
the  choice  of  a  camera,  or  disappointment  may  ensue.  Of  the 
working  of  a  detective  or  hand  camera  but  little  need  be  said  ; 
but  still  it  is  just  as  well  for  the  following  points  to  be  con- 
sidered. In  most  cases  comparatively  wide-angle  lenses  are 
used,  and  these  tend  to  dwarf  the  distance  and  give  exaggerated 
perspective.  Do  not  be  disappointed,  therefore,  if  instantaneous 
pictures  of  distant  mountains  or  other  objects  appear  as  insigni- 
ficant in  size  ;  plates  exposed  indiscriminately  on  all  sorts  of 
subjects  do  not,  as  a  rule,  yield  pictures,  though  they  may  produce 
perfect  negatives.  Subjects  with  very  great  contrasts  of  light 
and  shade,  such  as  street  views,  one  side  of  which  is  generally 
in  shadow,  do  not  yield  perfect  results  ;  and  rapidly  moving 
objects,  such  as  horses  or  men,  may  be  taken  in  too  brief  a 
period  of  time,  and  the  results,  though  perhaps  scientifically 
accurate,  are  not  truthful  as  we  see  them,  because  the  eye 
receives  an  impression  of  several  movements  combined  in  one. 
Of  the  plates  to  be  used  any  good  brand  is  suitable.  There  are 
several  points  in  connection  with  hand-camera  work  which  should 
be  noted.  First  as  to  holding  the  camera.  Some  workers  ad- 
here to  the  method  of  holding  the  camera  under  the  arm  pressed 

T  TO 


DICTIONARY  OF  PHOTOGRAPHY.  [Det 

close  against  the  body,  and  use  the  small  finder  to  judge  of  the 
position  of  the  object ;  others  hold  the  camera  under  the  chin 
and  sight  along  the  top.  The  best  position  depends  upon  the 
position  of  the  object  to  some  extent.  Suppose  we  wish  to  get 
a  shot  at  a  person  or  group  about  ten  feet  off,  placing  the  camera 
under  the  chin  will  probably  cut  off  his  feet,  whereas  holding  it 
under  the  arm  may  include  all  the  figure.  Then,  again,  suppos- 
ing the  object  to  be  a  distant  scene,  such  as  would  be  taken  from 
a  steamer  going  down  the  Thames  ;  in  this  case  holding  the 
camera  under  the  arm  will  include  far  too  much  foreground.  A 
method  for  which  I  am  indebted  to  a  well-known  optician  has 
proved  in  my  hands  exceedingly  useful.  It  is  : — When  the  object 
is  within  about  ten  or  fifteen  feet,  hold  the  camera  close  to  the 
body,  with  both  arms  at  full  length ;  this  places  the  camera  low, 
includes  a  lot  of  foreground,  and  obviates  any  chance  of  cutting 
off  any  one's  feet.  Supposing  the  object  to  be  taken  is  about 
twenty  feet  distant,  then  the  camera  may  be  held  against  the 
chest ;  if  the  object  is  about  thirty  feet  off  the  camera  may  be 
held  up  to  the  chin ;  but,  supposing  we  are  working  from  the 
deck  of  a  steamer  or  from  such  a  position  that  there  is  a  lot 
of  unnecessary  foreground,  then  by  raising  the  camera  level  with 
the  eye  and  the  arms  at  full  length  we  cut  off  a  lot  of  foreground, 
and  there  is  not  the  slightest  difficulty  in  seeing  whether  the 
camera  is  level  and  whether  we  include  the  desired  object.  If 
there  is  any  difficulty  on  this  point  we  may  use  one  or  two  sights, 
like  the  back  and  fore  sights  of  a  rifle.  I  beg  leave  to  enter  a 
protest  here  against  the  craze  for  working  shutters  at  unneces- 
sarily high  speeds.  The  idea  with  many  workers  seems  to  be 
how  quickly  the  shutter  may  be  driven,  whereas  how  slowly  it 
can  be  used  should  be  the  real  aim,  in  order  that  full  exposure 
to  the  shadows  and  darker  portions  of  the  picture  may  be  given. 
A  brief  word  of  remonstrance  may  not  be  out  of  place  at  the 
absurd  requirements  of  some  workers.  They  expect  for  a  few 
shillings  to  obtain  a  hand  camera  which  will  enable  them  to  turn 
out  the  very  finest  work,  to  compete  with  that  done  by  cameras 
costing  as  many  guineas.  I  do  not  wish  to  decry  cheapness,  for 
I  have  myself  done  work  with  a  twelve-shilling  camera  quite 
equal  to  anything  done  by  a  twelve-guinea  one  ;  but  then  it  was 
only  by  recognising  the  capabilities  of  the  camera,  and  not  by 
expecting  it  to  do  impossible  things,  by  recognising  that  the  lens 

I T  r 


Dev] 


DICTIONARY  OF  PHOTOGRAPHY. 


was  working  at  a  small  aperture,  that  the  shutter  would  not  be 
suitable  for  the  finish  of  a  race  or  an  express  train  at  full  speed, 
etc.  Ignorance  of  the  capabilities  of  the  instrument  is  in  many 
cases  the  cause  of  disappointment.  For  judging  distances,  always 
a  difficult  matter  for  a  beginner,  the  simplest  plan  is  to  learn 
distances  from  his  ordinary  surroundings  :  for  instance,  take  the 
street  he  lives  in  ;  find  the  width  of  it  from  his  door,  or  window 
to  the  opposite  pavement,  to  the  centre  of  the  road ;  measure  the 
distances  down  the  street ;  and  by  constantly  counting  these  over 
in  his  mind  whilst  looking  at  them  he  soon  learns  to  judge  all 
distances  by  them.  Finally,  it  should  be  remembered  that  a 
hand  camera  is  not  an  instrument  devised  for  the  purpose  of 
taking  photographs  in  positions  which  are  likely  to  cause  derision 
of,  or  annoyance  to,  anybody  ;  they  are  merely  portable  cameras 
which  should  be  used  to  obtain  mementos  of  rapidly  moving 
scenes  and  persons,  and  for  universal  picture-making. 

Development.  As  the  developer  is  the  agent  which  renders 
the  latent  image  visible,  so  the  operation  of  using  the  developer 
is  termed  development.  Development  may  be  divided  into  two 
distinct  classes — physical  and  chemical.  If  we  have  a  wet 
collodion  plate  which  has  been  exposed  on  a  subject,  we  shall 
have  practically  a  film  of  silver  salt,  part  of  which  has  been 
affected  by  light  and  which  is  covered  with  adherent  solution  of 
nitrate  of  silver.  On  adding  a  solution  of  ferrous  sulphate  to 
nitrate  of  silver  we  get  a  precipitate  of  metallic  silver,  this 
precipitation,  however,  being  delayed  by  the  presence  of  organic 
acid  such  as  acetic  or  citric.  If  a  piece  of  clean  silver  wire  be 
placed  in  the  acidified  ferrous-sulphate  and  silver  solution,  the 
silver  is  slowly  deposited  from  the  solution  on  to  the  silver.  In 
the  case  of  the  wet  plate  the  sensitive  salt  of  silver  which  has 
been  affected  by  light  acts  precisely  in  the  same  way,  and  the 
nascent  silver  from  the  adherent  nitrate  solution  is  deposited  on 
the  light-affected  places  forming  the  image.  At  present  there  is 
no  proof  that  the  sensitive  salt  is  itself  reduced.  This  is  called 
physical  development.  At  the  present  time  when  dry  gelatino- 
bromide  plates  are  so  much  in  use  we  have  practically  another 
state  of  things.  In  this  case  the  sensitive  salt  affected  by  light 
is  itself  reduced  to  the  metallic  state  by  certain  chemicals.  In 
this  case  we  have  no  silver  nitrate  slowly  depositing  silver,  but 

112 


DICTIONARY  OF   PHOTOGRAPHY.  [DeX 

the  sensitive  silver  salt  itself  is  reduced,  hence  this  is  called 
chemical  development.  In  a  developer  there  are  four  essential 
ingredients:  (i)  the  developer  proper  ;  (2)  the  accelerator,  which 
hastens  the  action  of  the  developer  ;  (3)  the  restrainer ;  and  (4) 
the  solvent  or  water.  The  developing  agent  may  be  pyrogallol, 
hydroquinone,  eikonogen,  amidol,  metol,  etc.  The  accelerator 
is  usually  an  alkali,  ammonia,  or  the  hydrates  or  carbonates  of 
potassium  or  sodium.  The  restrainers  are  the  bromides  of 
potassium  or  sodium  citrates,  etc.  If  a  developer  of  normal 
strength  is  applied  to  a  plate  which  has  never  been  exposed  to 
light  and  allowed]  to  act  for  a  long  time,  it  will  be  found  that 
there  is  a  general  reduction  of  the  silver  salt ;  this  general  re- 
ducing action  is,  however,  less,  if  some  soluble  bromide  be  added 
to  it.  Frequently  a  sulphite  is  added  to  a  developer,  and  this  is 
useful  in  that  it  prevents  the  too  rapid  oxidation  and  consequent 
discoloration  of  the  developing  agent,  and  thus  prevents  stain- 
ing of  the  hands  and  gelatine  of  the  film.  Having  thus  far 
considered  the  main  points  of  development  we  may  consider  the 
chemical  theory  of  the  same  to  be  as  follows  : — The  latent  image, 
which  we  will  assume  to  be  sub-bromide  of  silver,  Ag.,Br, 
is  split  up  into  metallic  silver  and  bromine  ;  the  bromine  is  at 
once  absorbed  to  form  bromide  of  the  alkali  or  some  more 
complex  compound,  the  reducing  agent  or  developer  proper 
being  oxidised ;  but  if  the  action  were  to  cease  at  this  point,  the 
image  would  be  very  faint ;  the  metallic  silver  and  the  unacted - 
on  bromide  of  silver  react  and  form  more  sub-bromide,  which 
is  again  reduced  by  the  developer  to  the  metallic  state.  For 
convenience  sake  the  particular  modifications  of  the  various 
developers  is  arranged  for  different  cases  likely  to  occur  in 
practice  under  the  heads  of  the  different  developers. 

Deviation.  An  optical  term  to  denote  the  alteration  of  the 
course  of  a  ray  of  light  when  it  is  refracted  or  reflected  from  the 
surface  of,  or  when  passing  through,  anything. 

Dextrine  (Ger.,  Stiirkegnmmi ;  Fr„  Dextrine  ;  Ital.,  Destruia). 
Synonym  :  British  Gum.  C12H10O,0.  Is  made  by  heating  starch 
until  it  loses  its  gelatinous  property,  or  by  heating  it  in  the 
presence  of  a  dilute  acid,  when  it  becomes  soluble  in  hot  and 
cold  water.  It  is  usually  a  pale  buff  powder,  and  is  used  as  a 
substitute  for  gum.    (See  MOUNTANTS.) 

113  1 


Dia] 


DICTIONARY  OF  PHOTOGRAPHY. 


Diactinic.  A  term  applied  to  any  medium  through  which 
the  actinic  rays  of  light  can  pass.  Substances  which  allow  only 
non-actinic  rays  to  pass  are  termed  adiactinic. 

Dialyser.  This  is  sometimes  used  in  the  washing  of  emul- 
sions, and  can  be  prepared  as  follows : — Take  a  tin  with  a 
tightly  fitting  lid,  knock  out  the  bottom  and  top,  stretch  over  one 
end  of  the  tin  a  piece  of  parchment  paper,  and  fit  the  rim  of  the 
lid  over  it,  so  as  to  clasp  it  tightly  down.  It  is  used  by  floating 
it  in  a  vessel  of  distilled  water,  and  the  materials  to  be  dialysed 
are  placed  in  the  tin.  All  bodies  which  will  crystallise  will 
pass  through  the  septum  of  parchment  paper,  leaving  those  which 
will  not  crystallise  in  the  dialyser.  In  the  case  of  emulsions  the 
unnecessary  salts,  such  as  nitrate  of  potash,  etc.,  pass  through  the 
septum,  leaving  the  colloid  gelatine  holding  the  sensitive  silver  salt. 

Diameter.  Any  straight  line  passing  through  the  centre  of  a 
circle  and  touching  the  circumference  at  opposite  points  is  thus 
termed.  If  the  diameter  of  a  circle  is  known,  multiplying  that 
by  3-14159  will  give  the  circumference,  and  vice  versa;  and  the 
diameter  squared  and  multiplied  by  7854  will  give  the  area  of 
the  circle,  and  the  cube  of  the  diameter  multiplied  by  "5236  will 
give  the  solid  contents  of  a  sphere. 

Diaphragms  are  either  loose  plates  of  metal,  or  a  rotating 
metal  screen,  both  having  apertures  of  certain  diameters ;  or 
another  form  is  of  tongues  of  metal  actuated  by  an  external  pin 
or  ring,  which  can  be  closed  and  opened  out  to  any  desired  size. 
The  Iris  diaphragm  consists  of  thin  flat  tongues  of  metal  fastened 
to  a  ring  in  the  lens  mount,  by  means  of  which  the  aperture  of 
the  diaphragm  may  be  enlarged  or  diminished  by  turning  the 
ring  backwards  or  forwards,  causing  the  tongues  to  contract  or 
enlarge  the  opening,  the  use  of  which  obviates  all  chance  of 
losing  or  misplacing  the  diaphragms.  The  diaphragms  of  the 
ordinary  or  Waterhouse  pattern  can  be  pinned  together  by  a 
brass  rivet  just  by  the  tongue,  on  which  the  numbers  are 
stamped,  thus  lessening  the  chance  of  losing  them.  The 
influence  of  the  diaphragm  on  the  picture  is  great  and  of  con- 
siderable practical  importance,  not  only  on  the  character  of  the 
picture,  but  also  on  the  duration  of  exposure,  as  we  shall  see 
when  treating  of  that  subject.  The  influence  of  the  diaphragm 
on  the  character  of  the  image  transmitted  by  the  lens  is  seen 

114 


DICTIONARY  OF  PHOTOGRAPHY.  [Dia 

first  in  a  reduction  of  the  amount  of  light  admitted  by  the  lens 
secondly,  by  increase  of  the  marginal  definition  ;  and,  thirdly,  by 
increase  of  the  depth  of  Focus  (q.v.).  Diaphragms  are  very 
often  termed  stops ;  but  this  is  not  quite  correct,  as  a  stop  is 
placed  in  contact  with  the  lens,  and  a  diaphragm  some  distance 
from  it.  For  single  lenses  the  diaphragm  is  usually  placed  from 
\  to  A  of  the  focal  length  in  front  of  the  lens,  in  which  position 
it  limits  the  diameter  of  the  pencils  of  light,  and  causes  them  to 
cross  the  axis  at  the  aperture  of  the  diaphragm,  before  refraction. 
(See  Distortion.)  The  distance  of  the  diaphragm  is  in  many 
instances,  when  placed  in  front  of  the  lens,  the  cause  of  Flare 
(q.v.).  This  can  be  obviated  by  altering  the  position,  one-eighth 
of  an  inch  either  way  being  generally  sufficient  to  obliterate  it. 
In  all  symmetrical  doublet  lenses,  the  proper  position  of  the 
diaphragm  is  equidistant  between  the  two  combinations ;  in 
unsymmetrical  combinations,  the  position  is  proportionate  to 
the  foci  of  the  combinations.  For  general  use  the  following 
maxims  should  be  remembered  : — A  large  diaphragm  gives  a 
bolder  picture  than  a  small  one  ;  focus  with  the  largest  apertiu  r, 
then  insert  the  smaller  diaphragms  till  sharpness  is  obtained 
over  the  whole  screen.  The  smaller  the  itop  the  Ion  go  the  ex- 
posure, also  the  flatter  the  field  of  the  lens,  and  the  greater  the 
depth  of  focus.  It  is  customary  to  give  the  apertures  of 
diaphragms  definite  diameters;  that  is  to  say,  the  diameter  of 
the  diaphragm  apertures  should  be  a  definite  fraction  of  the  focal 
length  of  the  lens.  There  are  several  methods  adopted,  the  one 
in  general  use  being  the  ratio  aperture,  or  ffx  system.  To  find 
this  number  divide  the  focal  length  of  the  lens  by  the  diameter 
of  diaphragm — e.g.,  focal  length  of  lens,  8^  ins. ;  diameter  of 
diaphragm,  |  in.;  8J-rJ=ir3;  number  of  diaphragm, //1 1-3. 
The  Photographic  Society  of  Great  Britain  number  the  dia- 
phragms, however,  in  rather  a  different  way,  taking  f\\  as  the 
standard,  which  they  call  No.  I.  This  system  is  termed  the 
"  Uniform  Standard,"  or  U.  S.  No.,  and  the  U.  S.  number  for 
any  diaphragm  marked  on  the  f/.v  system  may  be  found  by  the 
following  rule : — Divide  the  focal  length  of  lens  by  diameter  of 
diaphragm  to  find  fx,  square  the  result,  divide  by  sixteen,  and  the 
result  will  be  the  U.  S.  No.  Ex. :  Find  U.  S.  No.  of  diaphragm 
marked  //iT3.  113X  11*3  =  127-69  ;  127-69-7- 16  =  7*98,  or 
practically  8,  U.  S.  No.    (See  also  Appendix.) 

"5 


Dia] 


DICTIONARY  OF  PHOTOGRAPHY. 


In  1882  Dr.  Stolze  suggested  a  system  of  diaphragm  numbering 
which  was  found  by  squaring  the  focal  length  and  dividing  this 
by  the  diameter  of  the  diaphragm  squared  ;  thus,  taking  as  an 
example,  a  lens  of  81-in.  focus  and  diaphragm  apertures  of 
jtV>  £  x  H  m-f  we  should  find  the  numbers  as  follows : — 

(8^x8^(1^x1-^)=  64. 

(8*x8*)-H   t*    *)  =  I28. 

(8**8i)-M  ttx  «)  =  256. 
In  1886  Dr.  Stolze  suggested,  as  an  improvement  on  this,  the 
marking  of  the  stops  with  numbers,  obtained  by  dividing  the 
square  of  the  focal  length  by  one  hundred  times  the  square  of 
the  aperture,  e.g. : — 

(81  x  81)  -f-  (iTV  x  iTV)  100  =  -64 

(8£x8£)-f(   fx    i)  100  =1.28 

(8lx81)  +  (  l|x  ft)  100  =  2.56 

This  practically  means  taking  //io  as  the  unit,  which  aperture 

was  also  adopted  by  the  International  Congress  on  Photography, 

held  at  Paris  in  1889.    Mr-  T.  R.  Dallmeyer  recommended  the 

marking  of  the  diaphragms  on  a  system  which  takes  as  its  unit 

1  I  •  •'  •  \ 

—7=  =  tttz-.  The  diaphragms,  numbered  on  this  system,  would 
v'io     3  1D 

then  be  as  follows : — 

8£-t-ixV=  8   x  8    =64     -~io=  6.4. 

81  -r    |=  113  x  n  «3  ==  127-69-7- 10  =  12769. 

81 -f-  i ^  =  16  x  16  =256  -^10  =  25-6. 
It  will  be  seen  from  this  that  the  system  is  practically  a  modifi- 
cation of  Stolze's.  Zeiss,  the  famous  Jena  optician,  has  adopted 
yet  another  system,  which  takes  as  its  unit  fj  100,  as  suggested 
by  Dr.  Rudolph,  and  the  actual  working  aperture  of  the  lenses 
is  taken  as  the  diaphragm  aperture.  The  following  table  gives, 
therefore,  the  connexion  between  the  relative  or  ratio  aperture 
and  the  stops  : — 


No.  of  Stop. 

Relative  Aperture. 

No.  of  Stop. 

Relative  Aperture. 

1/100 

32 

I/I8 

2 

I/7I 

64 

r/12'5 

4 

I/50 

128 

1/8 

8 

1/36 

256 

1/6-3 

16 

1/25 

512 

i/4'5 

116 


DICTIONARY  OF  PHOTOGRAPHY. 


[Dia 


The  photographic  exposure  corresponding,  cater  is  paribus,  to 
the  different  stops,  is,  therefore,  in  the  inverse  ratio  of  those 
numbers.  Goerz,  the  optician  of  Berlin-Schoneberg,  has  adopted 
yet  another  system  of  marking  the  diaphragms  ;  this  is  the 
relative  time  of  exposure  (/)  calculated   from  the  formula 

/=  ^{^j  .when  /  =  the  focus,  d  —  effective  aperture.    This  is 

i 

really  Dallmeyer's  system  of  — ==(  but  the  diaphragms  are  num 

-•/io 

bered  differently.  The  following  table  shows  the  fjx  number 
for  each  diaphragm,  as  marked  by  Goerz  : — 


4  =  //6-3 

6  =  f/7'7 

12  =  //II 

24  =  //i5'5 


48  =//2i-9 

96  =  7/31 

192  =  //43-S 

384  =  //62. 


We  have  stated  above  that  to  determine  the  value  of  the 
diaphragms  it  is  necessary  to  find  the  focal  length  and  divide 
this  by  the  aperture  of  the  diaphragm.  Burton  gives  a  very 
convenient  table  in  his  useful  little  handbook,  "  Modern  Photo- 
graphy," which  gives  the  diameter  of  the  stop  aperture  for  lenses 
of  any  focus  from  6  to  1 1  in.,  and  the  diameter  of  any  aperture 
for  lenses  of  less  or  longer  focus  may  be  found  by  multiplying  or 
dividing,  as  the  case  may  be.    I  here  insert  this  useful  table  : — 


Focal  Length. 


Stan- 

fjx OR 

dard 

6  in. 

6i  in. 

7  in. 

7$  in. 

8  in. 

8}  in. 

9  in. 

9*  in. 

10  in. 

11  in. 

Ratio 

No. 

No. 

•25 

3'° 

3"25 

3'5 

3'75 

4-0 

4*25 

4'5 

4'75 

5'o 

5"5 

A* 

7/4 

•5 

2-I2 

2'3 

2-47 

2*65 

2-82 

3*oi 

3-x8 

3-36 

3'53 

3-89 

V£ 

1*62 

i"75 

1-87 

2'0 

2'12 

225 

2'37 

2-5 

2*75 

2 

I'OO 

1-23 

1-32 

1-41 

I*50 

*  "59 

i-68 

1-77 

1 -94 

y/s-656 

4 

•75 

•81 

•87 
•62 

•93 

I'O 

i*o6 

I'I2 

x-i8 

1-25 

i*37 

m 

8 

•53 

•57 

•06 

•71 

'75 

•80 

•84 

•88 

•97 

.//"•si 

16 

•37 

•40 

*44 

•47 

•5 

"53 

•56 

•59 

•62 

•69 

he 

32 

•26 

•28 

'31 

'33 

•35 

•38 

•40 

'42 

•44 

'49 

7/22*62 

64 

•188 

•20 

•22 

•23 

•25 

•26 

•28 

•29 

•31 

'34 

y/32 

128 

•132 

•144 

■iS5 

•168 

•177 

•188 

•20 

•21 

•22 

•24 

y/45'25 

256 

•094 

•101 

•109 

•117 

•125 

•i33 

•141 

•148 

•iS6 

•172 

y/64 

Now  for  an  example  or  two  how  to  use  this  table.  We  have 
a  lens  of  5-in.  focus,  and  want  to  cut  our  diaphragms  for  //8, 

117 


DICTIONARY  OF  PHOTOGRAPHY. 


//II'3>  f/1^  fl22>  aRd //32-  Turning  to 
the  table,  we  find  no  5-in.  lens  included, 
but  we  find  a  10-in.  ;  therefore  we  have 
the  diameters  there  given.  Carrying  the 
eye  down  the  column  under  10-in.,  we  find 
opposite  //8,  1-25,  then  -88,  '62,  -44,  -31, 
so  that  we  must  cut  our  apertures  to 
1-25  —  2  ==  -625  in.,  -88  -f-  2  =  -44  in., 
•62  ~  2  =  -31  in.,  and  so  on.  Where  the 
focus  of  the  lens  is  given  in  the  table  we 
merely  take4  the  apertures  there  given. 
To  some  it  may  be  difficult  to  accurately 
measure  the  diameters  of  apertures,  and  to 
facilitate  this  I  include  a  diagram  (fig.  81) 
taken  from  the  "  American  Annual  of 
Photography."  Each  cross  line  varies  in 
length  from  the  adjacent  one  by  i^th  of 
an  inch.  To  use,  lay  the  stop  flat  on  this 
scale,  and  select  a  cross  line  which  is  of 
the  same  length  as  the  greatest  diameter 
of  the  opening ;  read  this  off  by  means  of 
the  figures,  which  will  be  the  measure- 
ments in  y^ths  of  an  inch.  The  equivalent 
focal  lengthof  lens,  divided  by  this  measure- 
ment of  the  stop  opening,  will  give  the 
fraction  expressing  relative  rapidity  of  lens 
— //4,  or  whatever  it  may  be.  Personally, 
I  have  had  a  piece  of  thin  brass  cut  exactly 
to  measurement,  and  thus  ruled  and  con- 
tinued till  at  its  widest  part  it  measures 
four  inches.  By  inserting  this  in  a  stop, 
one  is  able  at  once  to  read  off  the  diameter, 
and,  dividing  the  focal  length  by  it,  to 
obtain  the  f/x  number.  The  following 
convenient  diagram  and  table  were  given 
some  years  back  in  the  "  British  Journal  of 
Photography  Almanack  ": — 

The  Photographic  Society  s  Standard 
Diaphragms, — The  annexed  diagram  and 
table  are  intended  to  facilitate  the  calcu- 

118 


DICTIONARY  OF  PHOTOGRAPHY. 


[Dia 


lation  of  the  proper  number  with  which  to  mark  the  diaphragms 
according  to  the  Photographic  Society  of  Great  Britain's  Uniform 
System,  which  will  be  found  described  on  another  page.  This 
number  it  is  proposed  to  call  the  ''  U.  S."  (or  uniform  system 
number).  The  numbered  circles  in  the  diagram  represent  the 
sizes  of  stops.    The  photographer,  knowing  the  equivalent  focus 


Fig.  24. 


of  his  lens,  Jooks  along  the  line  opposite  the  number  which 
represents  the  circle  nearest  inside  to  his  diaphragm,  and  when 
he  gets  to  the  column  headed  by  that  equivalent  focus  the  number 
there  found  is  the  U.  S.  number  to  be  marked  on  the  diaphragm. 
For  example,  a  lens  of  eight  inches  equivalent  focus  has  a  dia- 
phragm in  size  about  No.  5  on  the  diaphragm.  Running  the  eye 
along  the  line  opposite  No.  $,  we  find  in  the  column  under 

T19 


Dia]  DICTIONARY  OF  PHOTOGRAPHY. 

"  focus  eight  inches "  the  number  II,  which  is  the  U.  S.  number 
required. 


"si 

■j) 
0 

3 

w 
3 

uj 
3 

Cfl 

3 

n 
3 

V) 

3 

to 

3 

n 
3 

No. 

Circ 

.0 

SJ 

in 

w 
<o 

VO 

.2 
t>. 

w 

<2 

CO 

1 

0* 

0 

a 
0 

0 

u 
<2 
>* 

I      II  25 

39 

56 

1        1  1 

1 

2 

11 

17 

25 

34 

44 

*6 
j 

68 

1 

■2 
3 

1 
1 

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It  has  been  stated  above  that  the  ratio  aperture  of  diaphragms 
could  be  found  by  dividing  the  focal  length  by  the  diameter  of 
the  aperture.  This  is  practically  accurate,  but  not  scientifically 
so.  Where  the  diameter  of  either  or  both  of  the  lens  combina- 
tions is  less  than  the  fixed  stop,  the  diameter  of  the  combination 
is  the  actual  aperture ;  where  there  is  a  fixed  stop  or  a  ring  of 
metal  in  the  interior  of  the  lens  mount,  the  diameter  of  this  is 
the  actual  maximum  aperture.  These  ratio  apertures  are  strictly 
accurate  when  the  lens  is  a  single  landscape  lens  ;  but  with  all 
doublet  lenses  the  condensation  of  the  light  by  the  front  com- 
binations must  be  taken  into  account — especially  when  comparing, 
either  for  scientific  or  lens-testing  purposes,  the  actual  ratio 

120 


DICTIONARY  OF  PHOTOGRAPHY 


[Dia 


apertures,  practically  we  are  testing  the  effective  or  working 
apertures  of  the  lens.  This  is  by  no  means  a  difficult  operation, 
and  one  of  two  plans  may  be  adopted.  The  first  is  to  rack  the 
lens  out  to  its  equivalent  focus,  and  to  replace  the  ground-glass 
or  focussing-screen  by  a  piece  of  cardboard  or  thin  metal  plate, 
in  the  centre  of  which,  and  central  with  the  axis  of  the  lens,  is 
punctured  a  minute  pinhole.  The  camera  should  now  be  taken 
into  a  dark  room,  and  a  lighted  candle  placed  close  to  the  pin- 
hole in  the  cardboard.  On  examining  the  front  lens,  a  circle  of 
light  will  be  faintly  visible,  or  may  be  rendered  still  plainer  by 
breathing  on  the  lens  or  dusting  it  with  a  little  French  chalk  or 
plain  powder.  A  pair  of  dividers  may  be  used  for  taking  the 
diameter,  and  this  may  be  at  once  read  off  on  applying  the  same 
to  a  foot  rule,  and  the  focal  length  divided  by  this  will  give  at 
once  the  true  aperture  of  the  stop.  The  second  plan  is  by  the 
aid  of  a  simple  mathematical  calculation  as  follows  : — 
Let  D  =  the  true  aperture  value. 

d  —  actual  diameter  of  diaphragm  aperture. 

/=  the  focus  of  front  combination. 

/  ==  the  distance  between  the  plane  of  diaphragm  and 
the  centre  of  the  front  combination,  which  centre 
is  situate  midway  between  the  front  and  back 
surfaces  of  such  lens. 

Then 

(I.)  D  =  d  x  J-t 
(II.)  d=  D 

To  many  doubtless  this  is  all  Greek.  An  example  may  make 
it  plainer.  Let  us  suppose  we  have  a  Euryscope  lens  of  n-in. 
focus,  the  focus  of  the  front  combination  is  21  in.,  the  distance 
between  the  centre  of  combination  and  plane  of  diaphragm  is 
1^  in. ;  we  want  to  calculate  the  value  of  a  diaphragm  1  in.  in 
diameter ;  then,  substituting  the  above  values  for  the  letters,  we 
find 

~               21  21  . 

/)  =  1  x   =  1  x  —  =  1-0632  =11  in.  nearly. 

Therefore  our  stop  of  i-in.  actual  diameter  has  a  true  aperture 
value  of  ixV  in. ;  not  much  difference,  it  is  true,  but  still  sufficient 

121 


DiaJ 


DICTIONARY  OF  PHOTOGRAPHY. 


to  render  accurate  scientific  work  an  impossibility.  It  may 
happen  that,  by  this  calculation,  we  find  this  true  aperture  value 
greater  than  the  diameter  of  the  front  lens ;  if  this  is  the  case, 
the  diameter  of  the  lens  is  the  true  value.  Now  suppose  we 
have  a  lens  of  16-in.  focus,  and  wish  to  cut  our  diaphragms  to 
have  a  value  of  //8,  f/iv$i,  f/16,  etc.  We  know  that  //8 
should  be  2  in.  if  we  disregard  the  condensing  power  of  the 
front  lens  ;  the  focus  of  front  lens  being  30,  and  the  distance  from 
the  centre  of  this  lens  to  diaphragm  plane  1  in.,  we  get  then 

d  =  2  x        1  —  2  x  ?2  =  it4  actual  diameter  of  //8. 

30  30       lo'  Jl 

Then  for // 1 1  -3 1  we  shall  get 

7     ,  ,            x     30—1  29  : 

d  =  (16  —  1 1*31)  x  =  1*41  x    -  =  1-363  =  ll  in. 

It  is  true  these  measurements  show  but  little  difference  to  the 
actual  diameter  of  stop,  but  in  portrait  lenses  the  difference  is 
greater,  and  even  in  small  diameter  lenses  the  difference  is 
sufficiently  large  to  be  taken  into  account  when  testing  lenses. 
In  practice  it  will  be  necessary  to  calculate  out  the  true  diameter 
of  diaphragms  for  the  first  two  only,  the  smaller  diameters  being 
obtained  by  dividing  by  2,  4,  etc.  Another  method  of  making  the 
necessary  allowance  of  the  condensation  of  the  light  by  the  front 
lens  is  to  cut  the  stops  in  fractions  of  a  focus  less  than  the  true 
focus  of  the  lens,  and  this  may  be  found  in  the  following 
manner : — 

Let  F  —  the  equivalent  focus. 

/  =  the  focus  of  front  combination. 

/  =  the  distance  between  centre  of  front  lens  and  plane 

of  diaphragm. 
A  =  the  assumed  focus. 

Then 

k  =  fJ-=±. 

Or  to  take  the  example  given  above,  viz.,  a  lens  of  16-in.  focus, 
front  lens  focus  30  in.,  the  distance  from  lens  to  diaphragm  plane 
being  1  in.,  we  get 

a  t        30—I  r  21 

A  =  16  x  £  =  16  x  -  =  14-13. 

3°  $6 

T2'2 


DICTIONARY  OF  PHOTOGRAPHY. 


[Dia 


We  therefore  cut  our  apertures  for  a  I4*i3-in.  focus  instead  of  16-in. 
focus.  There  is  one  point  in  connection  with  diaphragms  which  it 
is  essential  to  note,  and  that  is,  the  ratio  aperture  is  calculated  from 
the  equivalent  focus,  but  that  in  photographing  near  objects,  such 
as  portraits  or  line  subjects,  we  have  to  rack  out  the  camera 
considerably,  and  that  therefore  the  ratio  aperture  of  any  given 
diaphragms  decreases  in  proportion  to  the  racking  out.  An 
example  will  make  this  plainer,  perhaps — for  reproducing  a 
diagram  full  size  with  an  8^-in.  focus  lens.  The  distance 
between  the  lens  and  focussing  screen  must  be  17  in.  We  have 
found  that  a  diaphragm  marked  //16  will  give  the  requisite 
sharpness,  but  this  aperture  is  calculated  from  the  equivalent 
focus.  Therefore,  as  the  diameter  of  the  aperture  of  the  dia- 
phragm remains  constant,  it  is  obvious  that  it  cannot  now  be 
fj\6  ;  we  must  therefore  calculate  out  afresh  the  ratio  aperture: — 
The  stop  is  marked  fj\6  and  is  ^  of  the  focal  length  =  8.1  in. 

.*.  Diameter  =  8^-7-16=  H. 
The  focus  when  copying  diagram  is  17  in. 

.'•  l7  +  Ih  ~  32»  tne  new  rati°  aperture  of  stop. 

Diazotype  or  Primulirie  Process.  This  is  a  process  patented 
in  1 89 1  by  Messrs.  Green,  Cross,  and  Bevan,  and  is  based  upon 
the  property  which  certain  diazotised  dyes  possess  of  being  so 
altered  by  light  that  they  will  not  form  colouring  matters  with 
certain  anilines  and  phenols.  As  various  colours  can  be  obtained, 
and  the  process  is  applicable  to  paper,  material  or  gelatine  on 
glass,  it  affords  a  ready  means  of  obtaining  decorative  material, 
although  the  colours  are  not  very  brilliant,  nor  is  the  ground  pure 
white.    The  solution  of  primuline  is  prepared  as  follows  : — 

Primuline     ...       ...       ...       ...       ...      10  parts. 

Distilled  water   1,000  ,, 

The  water  should  be  heated  to  near  boiling-point,  and  kept  at  this 
temperature  by  means  of  a  spirit  lamp  or  Bunsen  burner,  and  the 
primuline  added,  with  constant  stirring  till  dissolved.  In  this 
hot  solution  the  linen,  silk,  plush,  or  velvet — the  two  former  being 
deprived  of  their  dressing  by  washing — should  be  immersed,  and 
care  taken  that  the  dye  is  evenly  distributed  through  the  material 
by  pressing  with  glass  rods,  etc.,  and  stirring  about.  The 
material  after  about  five  minutes'  immersion  should  be  allowed 

123 


Dia] 


DICTIONARY  OF  PHOTOGRAPHY. 


to  drain,  rinsed  once  in  cold  water,  and  dried.  In  this  stage  it  is 
not  sensitive  to  light,  and  the  dipping  and  drying  may  be  effected 
in  daylight.  It  will  also  keep  well  in  this  condition.  The  drying 
should  be  rather  rapid,  and  therefore  blotting  off  between  blotting 
paper,  or  a  free  current  of  air,  should  be  resorted  to.  The  sen- 
sitising solution  is  composed  of 

Sodium  nitrite        ...       ...       ...        ...       4  parts. 

Oxalic  acid   6  ,, 

Distilled  water   1,000  „ 

In  this  the  material  should  be  immersed  and  well  saturated,  then 
drained,  rinsed,  and  superflous  moisture  removed  by  pressing 
between  thick  blotting  paper.  The  material  need  not  be  bone 
dry,  and  should  be  exposed  at  once,  as  it  will  not  keep.  The 
sensitising  and  drying  must  be  done  in  a  dark  room  or  by  weak 
gaslight.  As  this  process  is  what  is  called  a  negative  printing 
process — that  is,  it  yields  a  negative  from  a  negative — we  require 
a  positive  to  obtain  a  positive.  The  material  is  then  exposed 
under  a  positive  for  about  thirty  seconds  in  sunlight,  to  ten 
minutes  or  more  in  diffused  light.  The  process  of  printing  can 
be  gauged  to  some  extent  by  examining  the  material  in  the 
ordinary  way,  the  action  of  light  bleaching  the  material,  which 
assumes  a  dingy  colour.  It  is  advisable  till  practice  is  secured 
to  use  small  test  pieces  of  material,  exposing  them  side  by  side 
with  the  printing  frame  till  they  no  longer  give  colour  with  the 
developer.    The  developers  are  as  follows  : — 


/3-napthol    6  parts. 

Sodium  hydrate      ...       ...       ...       ...       8  ,, 

Distilled  water        ...       ...       ...       ...  1,000  ,, 

For  Yellow  Tones. 

Carbolic  acid  (crystal)    10  parts. 

Distilled  water   1,000  „ 


For  Red  Tones. 


For  Orange  Tones. 


Resorcin 
Sodium  hydrate 
Distilled  water 


6  parts. 


9  M 


...  1,000 


124 


DICTIONARY  OF  PHOTOGRAPHY. 


[Diff 


For  Purple  Tones. 


a-Napthylamin 
Oxalic  acid  ... 
Distilled  water 


,000 


12  parts. 
i'2  ,, 


For  Blue  Tones. 


Eikonogen 
Distilled  water 


...  1,000 


12  parts. 


For  Brown  Tones. 


Pyrogallol 


12  parts. 


Distilled  water   1,000  „ 

As  soon  as  the  colour  is  sufficiently  developed,  the  material 
should  be  well  washed  in  water,  and  dried.  Napthylamin  has 
an  intensely  disagreeable  smell,  which  may  be  removed  from  the 
hands  and  dishes  by  using  the  nitrite  sensitising  solution.  For 
purple  pictures  the  material  should  be  rinsed  in  dilute  solution 
of  tartaric  acid  and  dried  without  further  washing.  For  obtaining 
prints  on  paper  it  is  advisable  to  size  the  paper  well  first  with  a 
2  per  cent,  solution  of  gelatine  with  a  little  chrome  alum,  and 
allow  this  to  thoroughly  dry,  and  then  sensitise  by  floating  on  the 
hot  nitrite  solution,  care  being  taken  that  none  gets  on  the  back. 
The  after-treatment  is  the  same  as  for  materials.  Transparencies 
and  opals  can  be  made  by  coating  glass  with 

Primuline     ...       ...       ...       ...       ...      80  parts. 

Gelatine   480  „ 

Chrome  alum         ...       ...       ...       ...       2  ,, 

Distilled  water        ...       ...       ...  ...9,600 

allowing  to  set  and  dry,  and  then  sensitising  by  immersion  in  the 
nitrite  solution.  Prints  produced  by  this  process  are  permanent, 
unless  exposed  to  brilliant  sunshine.  Designs  in  different  colours 
can  be  made  by  thickening  the  developers  with  boiled  starch  and 
applying  with  a  brush.  Wool  and  silk  require  longer  exposures 
than  cotton  or  linen,  and  the  blue  and  purple  developers  are  not 
so  suitable  for  the  former,  and  for  these  two  instead  of  primuline 
dehydro-thiotoluidine-sulphonic  acid  is  recommended  as  giving  a 
purer  ground. 

Diffraction  or  Inflection.    An  optical  term  used  to  denote 


125 


DICTIONARY  OF  PHOTOGRAPHY. 


the  bending  of  the  rays  of  light  when  such  rays  pass  by  the 
edges  of  an  opaque  body.  The  effect  of  diffraction  on  the  waves 
of  light  is  exactly  the  same  as  that  peculiar  property  of  running 
water  of  curving  round  behind  an  obstacle. 

Diffused  Light.  Generally,  in  opposition  to  direct  light.  It 
is  the  only  light  which  should  be  used  for  Portraiture  (q.v.). 
Diffused  light  in  the  camera  is  generally  taken  to  mean  any 
actinic  light  other  than  that  passing  direct  on  the  plate  from 
the  lens.    It  is  a  certain  producer  of  fog. 

Dish.  One  of  the  most  necessary  articles  of  an  amateur's 
outfit.  It  is  made  of  various  materials :  glass,  earthenware, 
vulcanite,  metal,  and  wood  are  the  most  useful.  It  is  only 
necessary  to  say  it  should  be  kept  scrupulously  clean,  being 
occasionally  scrubbed  with  a  stiff  brush  and  some  strong  acid. 
One  dish  should  be  kept  specially  for  each  operation,  and  used 
for  that  only. 

Dispersion.  An  optical  term  used  to  denote  the  separation 
of  a  ray  of  heterogeneous  light  by  refraction  into  its  component 
rays  of  different  refrangibility.  Different  transparent  media 
have  different  dispersing  powers,  or  different  powers  of  widening 
the  angle  between  the  red  and  violet  rays,  and  it  is  owing  to  this 
difference  of  dispersive  power  in  different  kinds  of  glass  that 
chromatic  aberration  is  eliminated. 

Dissolving  Views.    See  Magic-Lantern. 

Distance.  The  objects  in  a  landscape  farthest  from  the  eye, 
forming  a  background  to  the  scene  ;  and,  in  an  artistic  sense, 
the  representation  of  objects  rendering  an  idea  of  remoteness, 
obtained  by  the  due  observance  of  the  rules  of  perspective,  etc. 
(See  Aerial  Perspective.) 

Distilled  Water.  H20=i8.  Absolutely  pure  water  obtained 
by  vaporisation  in  a  still  or  retort,  and  subsequent  condensation 
of  the  vapour.  It  should  be  used  in  all  operations  of  photo- 
graphy, especially  in  the  manufacture  of  emulsions  and  ferrous 
oxalate  development. 

Distortion.  All  images  may  suffer  from  no  less  than  three 
kinds  ot  distortion,  (a)  distortion  of  perspective,  {b)  distortion  of 

126 


DICTIONARY  OF  PHOTOGRAPHY. 


[Dis 


parallel  lines,  and  (c)  distortion  of  marginal  lines  or  the  aberration 
of  thickness  of  the  lens. 

(a)  Distortion  of  perspective.  This  is  frequently  noticeable  in 
ordinary  work,  particularly  in  architectual  studies  where  lenses  of 
short  focus,  compared  to  the  size  of  the  plate  have  been  used.  In 
such  a  case  near  objects  look  exaggerated  in  dimension  compared 
to  others  more  distant,  when  the  prints  are  examined  at  the 
distance  of  normal  vision,  whereas  if  the  pictures  are  viewed  from 
a  distance  equal  to  the  focus  of  the  lens  this  is  not  seen. 

(b)  Distortion  of  parallel  lines.  Whilst  this  is  strictly 
speaking  a  distortion  of  perspective,  it  is  better  to  consider  it  as  a 
separate  subject,  because  it  is  solely  due  to  a  misuse  of  the 
camera.    When  a  lofty  object  has  to  be  taken  and  the  camera  is 


tilted  up,  unless  the  swing  back  be  used,  what  should  be  parallel 
lines  in  the  print  will  appear  to  converge  as  in  fig.  25. 

(c)  Distortion  of  marginal  lines  or  aberration  of  the  thickness  of 
lenses.  If  a  square  ruled  on  paper  be  examined  with  an  ordinary 
reading  glass  it  will  be  found  that  the  lines  instead  of  being 
straight  will  be  curved.  When  a  landscape  or  single  lens  is  used 
with  a  stop  in  front  of  it,  lines  falling  near  the  margins  will  be 
curved  outwards,  as  with  the  stop  in  this  position  the  low  er  part 
of  the  lens  forms  the  image  of  the  upper  part  of  the  object ; 
with  the  stop  behind  the  lens,  the  reverse  is  the  case,  and  the 
distortion  is  pincushion  shape.  From  this  it  is  obvious  that  by 
placing  a  lens  on  either  side  of  a  diaphragm  we  get  the  two 
distortions  curing  one  another,  and  hence  the  rectilinear  or  doublet 
lenses. 


127 


Div] 


DICTIONARY  OF  PHOTOGRAPHY. 


Divergent  Rays  in  optics  are  those  which  continually  recede 
farther  and  farther  from  one  another,  being  the  opposite  to  con- 
vergent.   All  concave  lenses  are  divergent.    (See  Lens.) 

Dodging  Negatives.  There  are  few  negatives  which  will  not 
be  improved  by  some  after  treatment.  Under  the  heads  of 
Intensification  and  Reduction  will  be  found  instructions  for  these 
processes  which  have  for  their  general  purpose  the  increase  of,  or 
reduction  of,  density  respectively,  but  in  many  cases  it  is  found 
that  one  portion  of  a  negative  is  so  dense  in  proportion  to  the 
rest  that  it  will  not  print :  to  improve  such  a  negative  we  may  use 
the  method  of  harmonising  Harsh  Negatives  {q.v.),  or  we  may 
locally  reduce  it  or  intensify  it.  To  locally  intensify  a  negative 
it  should  be  thoroughly  well  washed  free  from  hypo,  or,  if  dried, 
soaked  in  water  for  an  hour,  then  intensified  by  the  use  of  the 
uranium  intensifier  (see  Intensification),  then  rinsed  once 
or  twice,  and  an  alkaline  solution  such  as  i  :  20  solution  of 
carbonate  of  soda  may  be  applied  with  a  camel's  hair  brush  to  the 
dense  parts  of  the  negative ;  and  this  has  the  effect  of  dissolving 
the  uranium  intensification  and  leaving  the  dense  parts,  therefore, 
in  their  original  condition,  so  that  the  result  will  be  a  negative 
intensified  in  the  shadows  but  not  touched  in  the  high  lights.  If 
necessary  the  negative  may  now  be  dried,  and  the  high  lights  still 
further  reduced  by  the  local  application  of  Farmer's  ferridcyanide 
and  hypo  reducer.  Vidal  has  suggested  for  local  intensification 
or  as  we  call  it  dodging,  painting  over  the  dense  parts  of  a 
negative  with  asphalt  dissolved  in  benzine,  allowing  this  to  dry, 
and  then  dipping  the  plate  into  a  solution  ol  some  aniline  dye, 
like  aurantia,  chrysoidine  extra,  Bordeaux  red,  etc,  the  strength  of 
the  solution  and  the  stay  of  the  negative  in  the  same  being  of 
course  adapted  to  the  degree  of  intensification  required  ;  the 
gelatine  absorbs  the  colouring  matter,  and  thus  the  thin  parts  are 
locally  intensified.  If  afraid  to  treat  the  film  in  any  way  for  fear 
of  losing  it,  one  may  paste  the  back  of  the  negative  with  starch 
paste,  and  lay  it  down  on  a  flat  sheet  of  tissue  paper  with  slight 
pressure,  allow  to  dry  and  trim  the  paper  down.  We  have  now 
a  surface  on  which  we  may  work  with  a  crayon  and  stump,  with 
retouching  pencils  or  water  colour.  Another  method  is  to  coat 
the  back  of  the  negative  with  matt  varnish  which  has  been  stained 
deep  red  by  the  addition  of  some  aniline  dye,  or  yellow  by  dis- 

128 


DICTIONARY  OF  PHOTOGRAPHY. 


[Dry 


solving  gamboge  in  it.  When  the  varnish  is  quite  dry,  we  may 
scrape  it  off  with  a  sharp  penknife  over  those  parts  we  wish  to 
print  through  more  and  thus  get  better  results.  Local  reduction 
may  of  course  be  carried  out  by  exactly  reversing  the  directions 
for  some  of  the  above  processes,  but  enough  has  been  said  to 
point  out  the  method  of  procedure  to  any  intelligent  operator. 

Doublet.    This  term  is  applied  to  lenses  which  have  a  glass 
or  combination  at  each  end  of  the  lens  tube. 
Various  names  have  been  given  to  these  lenses,  or  to  slight 
modifications,  and  as  far  as  possible  I  include  a  list  of  them  : 

Antiplanatic  Orthoscopic  Rapid  doublet 

Aplanat  Panorthoscopic  Rapid  paragon 

Aplanatic  Pantographic  Rapid  symmetrical 

Autographic  Portable  symme-  Rectigraphic 

Euryscope  trical  True  view 

Hemispheric  Rapid  rectilinear,  Universal 
Orthographic           or  R.R. 
Orthopanactinic 

Drachm  or  Dram.   See  Weights  and  Measures. 
Drop  Shutter.    See  Shutter. 

Drying  Box.  A  light-tight  box  used  for  drying  plates,  etc., 
coated  with  a  sensitive  film.  There  are  many  different  kinds, 
but  the  following  will  answer  well : — Make  a  box  of  half-inch 
deal,  2  ft.  long  by  I  ft.  wide  and  I  ft.  deep,  with  a  door  opening 
at  one  side,  with  a  deep  fillet  to  prevent  the  ingress  of  light ;  at 
the  bottom  pierce  about  twelve  holes,  and  have  a  second  bottom 
made,  but  with  openings  at  the  side.  In  the  centre  of  the  top 
have  a  two-inch  gas  or  zinc  pipe  fixed  with  an  elbow  joint,  and 
in  the  bend  of  the  joint  insert  a  small  gas  burner,  so  as  to  cause 
a  draught  of  air  when  lit.  Anhydrous  chloride  of  calcium  may 
also  be  placed  upon  the  bottom  of  the  box.  The  interior  may  be 
fitted  with  stout  wire,  or  glass  shelves,  about  three  inches 
apart. 

Drying  Marks.  These  are  generally  irregular  wavy  marks 
seen  near  the  margins  of  dry  plates  or  sometimes  as  fairly  regular 
patches  which  are  of  different  density  to  other  portions  of  the 
negative,  and  are  caused  by  unequal  drying  of  the  coated  plates, 

129  K 


Dry] 


DICTIONARY  OF  PHOTOGRAPHY. 


those  portions  remaining  moist  longest  being  more  sensitive  and 
therefore  appearing  as  over-exposed.  Drying  marks  are  also 
caused  in  an  otherwise  perfect  negative  if  the  same  be  allowed 
to  dry  unequally  or  at  different  temperatures.  For  instance,  if  a 
\ot  of  plates  are  placed  in  a  drying-rack  close  together  and  left 
for  some  time  the  centres  will  not  dry  so  quickly  as  the  edges, 
and  unequal  density  is  caused;  or  if  part  of  the  negative  be 
allowed  to  dry  spontaneously  and  the  other  part  be  dried  by  the 
heat  of  the  fire,  or  by  the  aid  of  spirit,  marks  will  be  caused. 

Dry  Plates.  Glass  of  particular  size  coated  with  a  film  of 
gelatine  in  which  a  sensitive  salt  of  silver  is  emulsified.  These 
are  to  be  bought,  commercially,  so  perfect  in  preparation  that  but 
few  amateurs  will  be  tempted  to  coat  their  own,  but  the  formulae 
given  under  Emulsion  will  be  found  all  that  can  be  desired,  and 
the  manufacture  of  emulsion  is  an  education  which  all  operators 
if  time  and  circumstances  permit,  should  undertake.  It  is  advis- 
able for  all  workers  to  examine  the  plates  that  they  intend  to  use, 
especially  when  starting  on  a  tour,  to  determine  one  or  two 
points.  Plates  should  be  examined  as  to  whether  they  are  cut 
to  size  correctly  or  not,  whether  they  are  evenly  coated,  this 
being  done  by  holding  the  plate  or  one  or  two  plates  in  turn, 
before  the  dark-room  light,  and  seeing  whether  one  part  lets 
through  more  light  than  another.  Freedom  from  fog  is  another 
essential,  and  the  best  way  to  test  this  is  to  take  out  a  plate  from 
a  freshly  opened  packet  in  a  very  dim  red  light,  and  place  in  a 
dish,  and  develop  with  freshly  mixed  ferrous  oxalate  or  pyro-soda 
developers  of  normal  strength  for  the  normal  time,  and  then  see 
whether  it  be  free  from  fog  or  not.  With  regard  to  the  sensitive- 
ness of  the  emulsion  this  is  usually  determined  and  marked  by 
the  maker. 

Dusting-on  Process.   See  Powder  Process. 

Eau  de  Javelle  is  used  for  eliminating  the  last  traces  of  hypo 
from  the  film,  and  also  for  reducing  over-dense  negatives,  its 
action  being  due  to  the  free  chlorine  evolved.  It  can  be  made 
as  follows  : — 

Chloride  of  lime    2  ozs.  or    50  grms. 

Carbonate  of  potash         ...        4    „    „    100  ,, 

Water    40    ,,      1,000  c.cm. 

j  30 


DICTIONARY  OF  PHOTOGRAPHY. 


[Eff 


Mix  the  lime  with  30  ozs.  of  water,  dissolve  the  potash  in  the 
remainder,  boil,  and  filter. 

Ebonite.  A  modification  of  indiarubber  made  by  heating  it 
with  sulphur  under  pressure.  It  is  used  for  making  dishes, 
instantaneous  shutters,  etc.,  and,  though  brittle  and  affected  by 
heat,  answers  well,  from  its  great  lightness  and  hardness. 

Edging.   See  Safe  Edge. 

Effective  Aperture.  The  effective  or  working  aperture  of  the 
lens  is  that  portion  which  actually  comes  into  use  with  the  various 
diaphragms,  and  the  size  of  the  working  aperture  is  dependent 

A 


J 

Fig.  26. 

not  only  on  the  size  of  the  diaphragm,  but  also  on  the  distance  ol 
the  object ;  but  for  comparison  of  lenses,  and  in  the  ordinary 
course  of  testing  a  lens,  parallel  rays  only  are  considered  in 
estimating  the  effective  aperture.  According  to  Dr.  Stolze,  "  with 
any  but  parallel  rays  of  light,  such  as  those  proceeding  from  near 
objects  under  otherwise  equal  conditions  :  (1 )  with  single  lenses, 


P     A  P 


Fig.  27. 


with  diaphragm  in  front,  the  effective  aperture  increases  if  the 
distance  of  a  luminous  point  decreases ;  (2)  with  doublets,  with 
diaphragm  between  the  lenses,  the  effective  aperture  increases 
as  the  distance  of  a  luminous  point  increases."  The  above 
diagrams  show  very  clearly  how  the  working  aperture  of  single 
and  doublet  lenses  is  respectively  equal  to  and  greater  than  the 

131 


Elk]  DICTIONARY  OF  PHOTOGRAPHY 

diameter  of  the  diaphragm  aperture.  In  both  figures  f  is  the 
focus  of  parallel  rays,  r  ;  p  the  lens  ;  and  the  diameter,  cd)  in 
fig.  26  is  equal  to  ad,  the  diaphragm  aperture,  but  in  fig.  27  cd 
is  greater  than  a  b.  Directions  for  finding  the  correct  working 
aperture  have  been  given  under  Diaphragm. 

Eikonogen,  introduced  by  Dr.  Andresen  of  Berlin  in  1889,  is 
the  sodium  salt  of  amido-/3-naphthol-/3-sulphonic  acid,  and  has 
the  formula  C,0H15SO3NaOHNH2.  It  was  first  discovered  by 
Professor  Meldola  in  1881. 

No.  1. 

For  Portraits  and  Landscapes. 
Solution  A. 

Sodium  sulphite    4  parts. 

Distilled  water    60  „ 

To  this  solution  add 

Eikonogen      1  part, 

which  has  been  previously  finely  powdered  by  means  of  a  mortar, 
and  dissolve  by  shaking.  Should  a  mortar  be  wanting,  the 
solution  can  also  be  prepared  by  placing  the  salts  into  boiling 
water,  and  shaking  till  dissolved. 

Solution  B. 

Washing  soda    3  parts. 

Distilled  water    20 

Immediately  before  developing  mix  the  developer  as  follows: — 

Solution  A   3  parts. 

Solution  B   1  part. 

No.  2. 

For  instantaneous  work  (about  ^th-sec.  exposure). 
For  this  purpose  formula  No.  1  is  to  be  used,  with  the  exception 
that  the  crystallised  carbonate  of  soda  is  substituted  by  the  same 
quantity  of  carbonate  of  potash. 

No.  3. 

For  very  short  instantaneous  exposure  (r^tii  of  a  second),  or 
or  increasing  the  power  of  Nos.  1  and  2  for  under-exposed  plates. 

132 


DICTIONARY  OF  PHOTOGRAPHY. 


[Eik 


Sodium  sulphite    5  parts. 

Carbonate  of  potassium    2  ,, 

Eikonogen                                          ...  1  part. 

Boiling  distilled  water    30  parts. 

The  following  is  the  formula  for  the  fixing  baths  recom- 
mended : — 

Hyposulphite  of  soda    4  parts. 

Bisulphite   1  part. 

Distilled  water    20  parts. 

Or 

Hyposulphite  of  soda       ...       ...       ...  20  parts. 

Sulphite  of  soda  (neutral)   5 

Distilled  water    100  parts. 

Sulphuric  acid  (sp.  gr.  1*845)    1  part. 

For  bromide  paper  it  is  advised  to  soak  the  paper  after  exposure 
in  40  parts  of  water,  and  when  limp  add  10  parts  of  No.  3 
solution  ;  if  the  image  hangs  fire  add  more  of  the  solution.  For 
over-exposure  reduce  the  quantity  of  Solution  3.  Bromide  of 
potassium  should  not  be  used.  After  developing  wash  well,  and 
place  in  an  alum  bath  for  several  minutes,  whereupon  it  is^again 
fixed  and  washed.  The  author  has  used  the  following  with  good 
results  : — 

No.  1. 

Eikonogen   40  grs.  or      2*6  grms. 

Sodium  sulphite     ...       ...     40  „  26  „ 

Distilled  water       ...       ...      10  ozs  „      250  c. cm. 

No,  2. 

Soda  carbonate    400  grs.  or     26  grms. 

Caustic  potash       ...       ...     50  ,,  ,,  3-25 

Distilled  water    10  ozs.  ,,  250  c.cm. 

For  use  mix  equal  parts  ;  for  instantaneous  work  add  5  grs.  or 
•3  grm.  hypo  to  No.  2.  Eikonogen  is  not  easy  to  preserve 
in  solution,  or  to  get  in  solution,  its  solubility  being  low,  only 
about  seven  grains  per  ounce  of  water ;  and,  further,  its  avidity 
for  oxygen  is  so  great  that  it  readily  oxidises  and  turns  brown, 
even  in  solution  with  a  sulphite.    The  best  preservative  is  acid 

133 


Eik] 


DICTIONARY  OF  PHOTOGRAPHY. 


sulphite  of  sodium  or  an  acidulated  solution  of  soda.  A  good 
formula  for  stock  solution  is  Voight's,  as  follows : — 

Acid  Sulphite. 

Sodium  sulphite    170  grs. 

Distilled  water                            to  make  1  oz. 

Hydrochloric  acid  ...       ...       ...       ...  40  minims. 

Dissolve  in  the  above  order. 

Stock  Solution. 

Eikonogen   125  gr. 

Sodium  sulphite     ...       ...       ...       ...  625  ,, 

Distilled  water       ...       ...        to  make  25  ozs. 

Acid  sulphite  as  above    1  oz. 

Dissolve  in  the  above  order.  Another  convenient  formula 
is : — 

Eikonogen    ...       ...       ...       ...       ...    125  grs. 

Acid  sulphite  of  sodium    ...        ^  oz. 

Distilled  water    to  make     25  ozs. 

For  accelerators  we  may  use  either  caustic  alkalies  or  the  car- 
bonates ;  and  having  this  choice  gives  us  far  more  control  over 
our  negatives  than  would  otherwise  be  the  case.  For  ordinary 
work  it  is  not  advisable  to  use  the  caustic  alkalies,  and  carbonate 
of  soda  may  be  used  where  soft  results  are  desired,  whilst  potash 
gives  us  a  little  more  contrast  and  density.  One  of  the  most 
important  points  when  using  eikonogen  as  a  developer  is  the 
temperature  of  the  solutions.  At  320  F.  its  developing  power  is 
practically  none,  and  its  power  increases  with  the  rise  of  tem- 
perature :  the  temperature  ol  the  developer  should  be  about  650  F. 
to  obtain  the  best  results.  Briefly  formulating  a  method  of 
development  with  eikonogen,  we  arrive  at  the  following  conclu- 
sions : — Under-exposure  and  instantaneous  shots  :  Use  either 
of  the  caustic  alkalies ;  or  with  extreme  under-exposure  or 
very  sharp  snap-shots  use  a  one-solution  developer  compounded 
on  Warnerke's  formula,  which  is  as  follows : — 

Eikonogen   1  oz. 

Caustic  potash       ...       ...    1  „ 

Sodium  sulphite     ...       ...       ...       ...       2  ozs. 

Distilled  water  (boiling)    10  „ 

l34 


DICTIONARY  OF  PHOTOGRAPHY. 


[Eik 


We  have  deprecated  the  use  of  one-solution  developers,  but  as 
the  addition  of  caustic  alkali  enables  us  to  obtain  a  much  greater 
concentration  of  solution,  it  is  useful  for  instantaneous  work. 
The  above  solution  should  be  diluted  with  from  three  to  ten  parts 
of  water  as  required,  more  water  giving  softer  results.  Where 
only  slight  under-exposure  exists  the  use  of  a  mixed  accelerator 
of  caustic  and  carbonate  will  be  found  useful,  and  the  caustic 
may  be  increased  as  desired  or  found  necessary.  Normal  ex- 
posure :  For  portraiture,  carbonate  of  soda  should  be  used,  as  in 
all  cases  where  softer  effects  are  desired ;  for  outdoor  or  land- 
scape work,  carbonate  of  potash  should  be  used,  and  with  a 
small  addition  of  bromide  of  potash.  Over-exposure  :  in  cases 
where  over-exposure  is  known  to  exist,  practically  the  same 
method  of  development  may  be  adopted  as  with  pyro — viz., 
increase  of  bromide  and  reduction  of  accelerator,  which  should 
be  carbonate  of  potash.  We  have  given  some  formulae  for 
stock  solutions  of  eikonogen  ;  we  now  come  to  stock  accelerators. 

Carbonate  of  Soda  Accelerator. 

Carbonate  of  soda  300  grs. 

Distilled  water,  to  ...       ...       ...       ...      10  ozs. 

Carbonate  of  Potash  Accelerator. 

Carbonate  of  potash    1 50  grs. 

Distilled  water,  to   ...       ...      10  ozs. 

One  part  of  these  may  be  mixed  with  an  equal  quantity  of 
eikonogen  stock  solution  and  applied  to  the  plate.  The 
caustic  alkalies  should  only  be  used  in  cases  where  such  are 
indicated  as  above,  and  stock  solutions  may  be  prepared 
either  in  10  per  cent,  or  20  per  cent,  as  desired,  and  they 
should  be  added,  drop  by  drop,  so  as  to  avoid  frilling  and 
fogging  of  the  film.  A  good  all-round  accelerator,  which 
gives  excellent  results,  and  which  can  be  modified  with  extreme 
ease,  is  the  following  : — 

Carbonate  of  soda  ...       ...    400  grs. 

Caustic  potash    ...       ...      50  ,, 

Distilled  water,  to   20  ozs. 


One  part  of  this  may  be  mixed  with  an  equal  quantity  of  stock 

T35 


Ele] 


DICTIONARY  OF  PHOTOGRAPHY. 


eikonogen.  If  development  hangs  fire  at  all,  or  the  plate 
shows  signs  of  under-exposure,  add  gradually,  or  drop  by  chop, 
watching  the  action  after  each  addition — 

Caustic  potash    120  grs. 

Distilled  water,  to  ...       ...       ...       ...       1  oz. 

Of  the  application  of  eikonogen  to  lantern  and  bromide  work  we 
cannot  speak  at  present,  but  in  our  opinion  it  is  far  superior  to 
ferrous  oxalate  or  hydroquinone  for  this  purpose.  It  is  advisable 
when  using  eikonogen  to  employ  the  acid  fixing  bath,  as  obviating 
all  stains,  and  hardening  the  film  and  preventing  frills  and 
blisters,  which  are  liable  to  occur  when  forcing  plates  with  caustic 
alkalies.  The  superiority  of  eikonogen  over  pyro  and  hydro- 
quinone is  manifest,  particularly  in  developing  snap-shot  and 
portrait  work,  as,  no  matter  how  dense  the  high  lights  and  how 
weak  the  shadows,  the  resulting  prints  are  far  softer  and  more 
harmonious  than  would  be  the  case  with  the  other' two  reducing 
agents.  It  gives  an  image  of  a  bluish  black  or  grey  colour,  free 
from  any  brown  tinge,  as  is  the  case  with  pyro,  and  development 
has,  therefore,  to  be  carried  rather  farther  than  old  pyro  workers 
are  accustomed  to. 

Elemi.  A  concrete  resinous  exudation  from  Canwium  com- 
mune, a  native  of  Malay.  It  is  sometimes  used  in  the  preparation 
of  Varnish  (q.v.). 

Eliminator,  Hypo-.  Any  salt  or  solution  of  salt  used  to  get 
rid  of  the  last  traces  of  hypo  from  the  films  or  prints.  Many 
so-called  eliminators  have  been  recommended,  as  peroxide  of 
hydrogen,  eau  de  javelle,  alum,  acetate  of  lead,  hypochlorite  of 
zinc;  but  opinions  seem  to  be  about  equally  divided  as  to  the 
benefit  of  their  action. 

Emulsion.  Photographically,  a  mechanical  mixture  of  any 
sensitive  salt  of  silver  in  extremely  minute  division,  held  in 
suspension  in  any  viscous  vehicle,  such  as  gelatine  or  collodion, 
which,  when  spread  upon  any  transparent  medium,  shall  present 
a  perfectly  homogeneous  appearance  when  viewed  by  transmitted 
light.  It  would  be  unnecessary  and  impossible  to  write  a 
thoroughly  comprehensive  account  of  the  emulsion  processes ; 
for  such  a  work  the  amateur  must  consult  Eder's  "  Handbook  to 

136 


DICTIONARY  OF  PHOTOGRAPHY.  [EmU 

Emulsion  Photography,"  but  a  few  well-proved  formulae  will  be 
given.  The  material  upon  which  the  emulsion  may  be  spread 
may  be  either  glass,  paper,  or  any  special  substance  desired. 
The  emulsion  may  be  either  for  the  production  of  negatives, 
transparencies,  positives,  or  lantern  slides,  for  development  or 
printing  out.  In  this  article  that  intended  for  negative  work 
alone  will  be  treated  of.  To  summarise  all  the  methods  which 
have  been  suggested  for  emulsion  making  would  be  almost  im- 
possible, at  least,  within  reasonable  limits.  Practically,  however, 
we  may  consider  that  there  are  three  methods  in  general  practice, 
viz. — 

(a)  The  ammonio-nitrate  process. 
(d)  The  acid-boiling  process. 
(c)  The  cold  process. 

The  ammonio-nitrate  process,  which  may  be  briefly  described  as 
the  conversion  of  the  nitrate  of  silver  into  the  double  salt  by 
means  of  ammonia,  and  the  addition  of  this  to  a  bromised 
gelatine  solution,  and  digestion  of  the  emulsion  at  a  moderate 
temperature  for  a  given  period,  is  simple  and  easy  to  carry  out, 
and  the  one  specially  suitable  for  amateur  emulsion  makers. 
The  acid-boiling  process  requires  more  apparatus  than  the  previous 
one,  and  though  clean  working  plates  are  obtained,  the  sensitive- 
ness is  not  quite  so  great  as  with  ammonia.  The  cold  process  i 
is  simple  and  easy,  requires  no  heating,  but  it  is  far  more  difficult 
to  obtain  regular  results. 

(a)  The  Ammonio- Nitrate  Process.  Eder  was  the  first  to 
suggest  this  process,  and  the  following  is  his  latest  formula. 
Two  solutions  are  required. 

A. 

Potassium  bromide   ...      24  parts. 

Solution  of  potassium  iodide  (10  percent.)    3-8  ,, 

Hard  gelatine  (Winterthur)    20  ., 

Distilled  water    ...    250  ,, 

Allow  the  gelatine  to  soak  for  from  30  to  60  minutes  in  the  water 
in  a  closed  vessel,  then  place  the  vessel  in  a  water  bath  and 
allow  the  gelatine  to  dissolve,  and  add  the  haloid  salts.  Now 
place  the  thermometer  in  the  gelatine  solution,  and  make  the 

137 


Emu]  DICTIONARY  OF  PHOTOGRAPHY. 


same  register  400  C.  (—  1040  F.).  Should  the  emulsion  be  too 
cool,  raise  the  temperature  of  the  water  bath ;  if  too  hot,  place 
the  vessel  in  cold  water  for  a  little  time  till  the  emulsion  reaches 
the  desired  temperature. 

B. 

Silver  nitrate. . .    ...       ...     30  parts. 

Distilled  water   250  „ 

When  dissolved,  add  cautiously  liq.  ammonia,  -88o,  till  the  brown 
precipitate  first  formed  is  redissolved.  So  far  these  operations 
may  be  performed  in  daylight,  but  it  is  now  necessary  to  enter 
the  dark-room,  and  the  silver  solution  should  be  added  to  the 
bromised  gelatine  in  small  quantities  at  a  time,  vigorously  shaking 
between  each  addition.  The  total  time  of  mixing  must  not  be 
long,  as  otherwise  the  temperature  sinks  too  low.  Eder  states 
that  the  silver  solution  should  be  used  at  the  ordinary  temperature 
and  not  heated  ;  but  I  have  obtained  equally  good  results  by 
using  hot  water  for  dissolving  the  silver,  and  thus  using  the 
solution  warm.  As  soon  as  the  emulsion  is  mixed  it  should  be 
placed  in  the  water  bath,  the  temperature  of  which  should  be 
450  C.  (=  1 1 30  F.).  Eder  now  recommends  wrapping  the  vessel 
in  blankets,  flannels,  etc.,  to  retain  as  far  as  possible  an  even 
temperature.  By  using  a  very  faint  spirit  flame  or  gas  flame, 
however,  it  is  quite  possible  to  keep  the  temperature  the  whole 
time  at  45°  or  just  above.  It  will  be  noted  in  the  above 
formula  that  the  quantity  of  iodide  solution  is  not  definite — viz., 
3  to  8  parts.  According  to  Eder,  increase  of  the  iodide  up  to 
8  parts  gives  rather  more  sensitive  emulsions  which  are  less 
liable  to  halation  in  landscape  work.  Many  operators  prefer  to 
use,  for  portraiture,  an  emulsion  which  contains  little  or  no  iodide, 
and,  therefore,  the  amateur  plate-maker  can  take  his  choice. 
The  duration  of  the  digestion  of  the  emulsion  in  the  water  bath 
has  the  most  important  influence  on  the  final  sensitiveness  of 
the  emulsion.  When  the  above  emulsion  is  digested  for  about 
15  minutes,  a  slow  landscape  emulsion  registering  about  150  W. 
and  working  with  great  clearness  and  vigour  "will  be  obtained; 
with  30  minutes'  digestion  the  sensitiveness  will  be  about  17  to 
190  W. ;  with  45  minutes'  digestion  about  22  to  240  W.  During 
the  digestion  the  flask  must  be  shaken  two  or  three  times  so  as 
to  prevent  any  undue  separation  of  the  sensitive  silver  salts. 

138 


DICTIONARY  OF  PHOTOGRAPHY.  [Emu 

When  commencing  to  make  the  emulsion,  take  of  hard  gelatine 
15  to  20  parts.  Allow  this  to  swell  in  distilled  water,  and  as 
soon  as  the  emulsion  has  been  digested  pour  off  the  water  from 
the  gelatine,  allowing  it  to  drain  slightly,  and  carefully  let  it  melt 
in  the  water  bath,  which  it  should  readily  do,  as  in  the  course 
of  an  hour  or  so,  which  has  passed  in  the  above  operations,  it 
will  have  absorbed  enough  water  to  melt.  This  melted  gelatine 
should  then  be  added  to  the  emulsion  and  the  whole  well  shaken, 
then  the  froth  should  be  allowed  to  subside  a  little,  and  the 
emulsion  poured  out  into  a  flat  glass  or  porcelain  dish  to 
set.  The  emulsion  should  be  about  three-quarters  of  an  inch 
thick  in  the  dish,  and  should  be  placed  in  absolute  darkness  to 
set,  which  takes,  as  a  rule,  about  five  to  eight  hours,  according 
to  the  temperature.  In  the  height  of  summer  a  little  ice  placed 
in  the  same  box  as  the  emulsion  will  be  of  assistance ;  in  cold 
weather  this  is  not  necessary.  The  above  process  is  suitable 
for  plates  of  medium  sensitiveness,  and  it  is  just  as  well  to  state 
here  that  very  rapid  plates  are  extremely  difficult  to  make,  and 
fog  and  all  such  incidental  and  minor  troubles,  such  as  frilling, 
blisters,  spots,  etc.,  are  more  likely  to  make  their  appearance 
when  trying  to  make  rapid  plates.  The  simplest  formula  which 
the  writer  has  tried,  and  the  one  in  which  success  is  more  likely 
to  attend  a  novice's  efforts,  is  the  following  of  Eder's,  which  gives 
a  very  good,  clean  working  plate  of  about  1 50  W. : — 

A. 

Ammonium  bromide         ...    20  parts. 

Solution  of  potassium  iodide  (10  percent.)  3  ,, 

Hard  gelatine                                       ...  45  M 

Distilled  water       ...    300  ,, 

Allow  the  gelatine  to  soak  in  the  water  for  one  hour  ;  dissolve 
by  the  aid  of  a  gentle  heat ;  add  the  salts. 

B. 

Silver  nitrate      30  parts. 

Distilled  water        ...    300  ,, 

Dissolve  the  silver,  and  convert  into  the  ammonia-nitrate  by  the 
addition  of  ammonia  as  previously  directed.  Heat  solution  A 
t°  35°  C.  (=  940  F.),  and  add  solution   B ;   digest   for  30 

*39 


EmuJ  DICTIONARY  OF  PHOTOGRAPHY. 


minutes,  and  pour  out  to  set.  By  digesting  10  minutes  only  a 
very  fine-grain  emulsion  is  obtained,  which  gives  good  lantern 
slides.  The  proportion  of  iodide  solution  may  be  increased  from 
3  to  8  parts  with  advantage  when  the  plates  are  intended  for 
landscape  work  ;  but  in-this,  as  in  every  formula  where  the  iodide  is 
increased,  the  bromide  must  be  correspondingly  reduced,  which 
may  easily  be  done  by  referring  to  the  tables  given  at  the  end  of 
this  work.  Very  rapid  plates  are  not  easy  to  make,  but  in  order 
to  complete  this  note  we  may  briefly  indicate  how  to  prepare  the 
same.  The  formula  for  the  emulsion  may  be  precisely  the 
same  as  that  given  on  p.  137  ;  but  the  iodide  should  be  the 
full  quantity  of  8  parts,  and  the  bromised  gelatine  be  heated  to 
6o°  F.  (=  I40°.F.),  and  the  silver  solution  added  to  it,  and  after 
about  40  to  50  minutes'  digestion,  in  the  water  bath,  at  a  tem- 
perature of  400  C.  (=  104°  F.),  a  sensitiveness  equal  to  about 
230  W.  will  be  easily  obtained.  When  making  such  an  emulsion, 
it  is  advisable  to  cool  rapidly  and  wash  rather  quickly,  as  the 
digestion  at  such  high  temperatures  has  a  tendency  to  give  rise 
to  frilling  and  blisters.  Some  manufacturers  use  chrome  alum 
to  prevent  this  frilling,  and  it  is  possibly  due  to  this  that  some 
commercial  plates  require  so  long  to  develop  and  fix — not 
always  a  desirable  feature.  Chrome  alum  too  is  always  faintly 
acid,  and  tends,  therefore,  to  the  lowering  of  the  sensitiveness  ; 
this,  however,  may  be  avoided,  I  think,  by  neutralising  it  by  the 
cautious  addition  of  liq.  ammonia,  and,  so  far  as  I  have  been 
able  to  determine,  this  in  no  way  affects  the  hardening  action  of 
the  alum  on  the  gelatine.  On  the  other  hand,  if  the  chrome  alum 
solution  be  rendered  more  than  very  faintly  alkaline,  there  seems 
to  be  a  greater  tendency  to  fog.  Practically,  an  addition  of  20 
parts  of  a  2  per  cent,  solution  of  chrome  alum  to  every  1000  parts 
of  emulsion  will  not  be  amiss,  and  it  is  advisable,  if  it  is  desired 
that  the  plates  should  keep  long,  to  make  an  addition  of  15  to  20 
parts  of  a  1  per  cent,  solution  of  potassium  bromide  to  every  1000 
parts  of  emulsion  ;  these  additions  must  be  made  immediately 
before  coating. 

The  Acid-Boiling  Process.  The  disadvantage  of  not  being 
able  to  obtain  such  a  high  sensitiveness,  nor  such  great  regularity 
as  with  the  ammonia  process,  rather  places  this  hors  de  combat, 
one  well-known  writer  even  going  so  far  as  to  say  that  it  is 
impossible  to  obtain  good  plates  by  this  process.    Possibly  the 

140 


DICTIONARY  OF  PHOTOGRAPHY. 


[Emu 


best  answer  to  that  is,  that  it  is  used  by  a  well-known  firm  of 
plate  makers  to  prepare  excellent  plates.  The  following  is  the 
process,  devised  by  Mr.  Wilson,  which  won  a  prize  offered  by 
Mr.  Paget  in  1880. 

To  make  a  pint  of  emulsion  select  a  20-ounce,  narrow-mouthed 
stoppered  bottle,  with  a  well-fitting  stopper  and  thin  bottom. 
Make  it  perfectly  clean.    Make  a  stock  solution  of 

Hydrochloric  acid  (pure)    1  fl.  drm. 

Distilled  water    1 2A  ozs. 

Put  into  the  20-ounce  bottle 

20  minims  of  the  above  dilute  acid. 

3  fluid  ounces  distilled  water. 

210  grains  ammonium  bromide. 

80  grains  Nelson's  No.  1  photo,  gelatine. 

Leave  the  gelatine  to  swell  for,  say,  fifteen  minutes  or  longer. 
In  a  clean  glass  vessel  (beaker,  measure,  or  flask)  dissolve  330 
grs.  of  nitrate  of  silver  (re-crystallised)  in  3  ozs.  of  distilled  water. 
Pour  out  about  2  fluid  drms.  of  this  silver  solution  into  another 
small  vessel  (say  test  tube),  and  dilute  it  to  half  strength  with  an 
equal  quantity  of  distilled  water.  Take  the  20-ounce  bottle  and 
the  two  lots  of  silver  solution  into  the  dark-room.  Mr.  Wilson 
prefers  to  use  a  large  paraffin  lamp,  protected  by  one  thickness 
of  ruby  and  one  of  dark  orange  glass  to  two  thicknesses  of  dark 
orange  paper  without  any  ruby.  In  the  dark-room  have  a  gas- 
boiling  stove,  and  on  it  a  tin  pot  or  saucepan  deep  enough  to 
contain  the  bottle  when  the  lid  is  on.  It  should  have  a  tin, 
perforated,  false  bottom  to  prevent  the  bottle  resting  immediately 
on  the  true  bottom  ;  or  a  piece  of  wire  gauze  will  answer.  Let 
the  pot  contain  some  3  or  4  ins.  in  depth  of  boiling  water.  Turn 
out  the  gas  of  the  stove,  if  alight,  and  plunge  the  bottle  into  the 
water  two  or  three  times,  so  as  to  avoid  cracking  it  by  too  sudden 
heating ;  then  leave  it  in  for  a  few  minutes  until  the  gelatine  is 
completely  dissolved.  Do  not  leave  it  in  longer  than  necessary 
for  complete  solution.  Take  it  out,  shake  up,  remove  the  stopper, 
and  set  bottle  down  on  the  table  near  your  lamp,  so  that  you  Can 
see  what  you  are  doing.  Pour  in,  all  at  once,  the  4  drms.  of 
dilute  silver  solution.  Put  in  the  stopper,  and  shake  up  thoroughly, 
but  not  too  violently,  for  about  half  a  minute.     Now  pour  in  the 

141 


DICTIONARY  OF  PHOTOGRAPHY. 


strong  silver  solution  in  quantities  of  about  half  an  ounce  at.  a 
time,  shaking  as  before  after  each  addition,  and,  when  all  is 
added,  give  a  final,  thorough  shaking  for,  say,  a  couple  of  minutes. 
Now  put  the  bottle  into  the  pot  of  hot  water,  see  that  the  stopper 
is  not  jammed  in,  and  put  on  the  lid.    Light  the  gas,  and  boil  up 
as  quickly  as  possible.    If  the  water  was  previously  boiling,  and 
the  gas  only  turned  out  for  the  mixing  operations,  it  should  boil 
up  in  less  than  5  mins.  ;  then  keep  boiling  for  59  mins.    At  the 
end  of  this  time  turn  out  the  gas,  take  off  the  lid,  take  out  the 
bottle,  and  remove  the  stopper  at  once,  or  you  will  not  get  it  out 
afterwards.    The  bottle  must  now  be  cooled  down  as  quickly  as 
is  consistent  with  safety  to  the  glass.     In  very  cold  weather  it 
may  stand  on  the  table  for  10  mins.  or  so,  and  then  be  cooled 
with  water  ;  or,  in  any  weather,  place  it  in  a  pan  of  nearly  boiling 
water,  and  cool  gradually  by  allowing  cold  water  to  trickle  slowly 
in,  shaking  the  bottle  occasionally.    Whatever  method  is  adopted, 
it  should  be  down  to  900  F.,  or  lower,  in  J  5  or  20  mins.  at  the 
most.    It  cannot  easily  be  made  too  cold,  as  the  gelatine  has  lost 
its  power  of  setting.    In  a  glass  beaker  (about  12  or  14  ozs.  size) 
put  l  oz.  of  Nelson's  No.  1  Photographic  or  "  X  opaque  "gelatine, 
and  pour  over  it  10  ozs.  of  clean  ordinary  water.    Leave  it  to 
soak  until  the  gelatine  has  absorbed  4  ozs.  of  water,  pour  off  the 
surplus  6  ozs.,  melt  the  swelled  gelatine  by  immersing  the  beaker 
in  hot  water,  and  pour  it  into  the  20-ounce  bottle  containing  the 
cooled  emulsion.    Shake  up  well,  and  pour  all  back  into  the 
beaker,  draining  out  the  bottle  thoroughly.    Leave  it  to  set  in  a 
cool  place  for  24  hrs.    It  has  next  to  be  washed.    The  addition 
of  the  gelatine  after  boiling  should  be  made  when  the  boiled 
emulsion  and  dissolved  gelatine  are  both  at  as  low  a  temperature 
as  possible,  and  between  the  time  of  this  addition  and  that  of 
washing  the  emulsion  it  should  be  kept  as  cold  as  possible.  For 
the  washing  clean  ordinary  water  at  a  temperature  cooled  down 
to  below  40  degs.  by  melting  ice  in  it,  should  be  used.  In 
a  glazed  earthenware  pan  or  other  suitable  vessel  put  about 
3  pints  of  cold  water,  and  add  3  ozs.  of  saturated  solution  of 
potassium  bichromate  (made  by  saturating  clean  ordinary  water 
with  the  bichromate).     Before  squeezing  the  set  emulsion 
through  the  canvas  it  should  be  cooled  down  so  as  to  be  as 
firm  as  possible.     The  water  into  which  it  is  squeezed  will 
then  remain  almost  clear,  or  but  slightly  milky.    If  the  emul- 

142 


DICTIONARY  OF  PHOTOGRAPHY.  [EmU 

sion  be  soft,  even  though  the  water  be  ice  cold,  the  water  will 
be  more  milky,  and  the  emulsion  take  up  too  much.  Too 
much  excess  of  acidi  bromide,  too  high  a  temperature  at  the 
time  of  adding  the  gelatine,  or  keeping  at  too  high  a  temperature 
between  adding  and  washing,  will  produce  the  same  result. 
Having  cooled  the  beaker  of  set  emulsion  down  to  400  F.,  run  a 
bone  spatula  or  paper-knife  round,  and  turn  out  the  emulsion,  or 
cut  it  out  in  lumps.  If  cold,  it  will  come  out  almost  quite  clean 
from  the  glass.  Place  it  on  a  piece  of  coarse  "  straining  cloth  " 
or  canvas,  and  squeeze  through  the  meshes  into  the  water,  the 
operation  being  performed  under  the  surface  of  the  water. 
Leave  it  so  for  an  hour.  Lay  the  straining  cloth  over  the  mouth 
of  another  pan  or  large  jar,  and  pour  the  mixture  of  emulsion 
threads  and  liquid  on  to  it  so  as  to  let  the  latter  run  through. 
Squeeze  the  emulsion  a  second  time  through  the  cloth  into  clean 
cold  water,  and  immediately  repeat  the  operation  for  a  third  time, 
leaving  the  emulsion  in  the  last  water  for  half  an  hour.  When 
strained  for  the  last  time,  place  cloth  and  all  in  a  large  beaker, 
and  put  the  latter  into  hot  water  until  the  emulsion  is  completely 
melted  and  warmed  to  about  115°  F. — i.e.,  not  warmer  than  is 
pleasant  to  the  hand.  With  a  clea?i  hand  take  out  the  cloth  and 
squeeze  it ;  very  little  will  be  lost.  The  emulsion  should  now 
measure  about  16  or  17  ozs.  Add  2  ozs.  of  alcohol,  and  mix 
thoroughly.  The  alcohol  may  be  either  pure  ethylic  alcohol, 
sp.  gr.  about  "830,  or  good  colourless  methylated  spirit.  If  the 
emulsion  now  measures  less  than  20  ozs.,  make  it  up  to  that  by 
adding  clean  water.  The  emulsion  is  now  ready  for  use.  It 
should  be  filtered  into  the  coating-cup  through  cotton-wool  to 
free  from  bubbles,  and  plates  coated  in  the  usual  way,  dried  and 
used  as  usual  for  rapid  gelatine  plates,  using  about  an  ounce  of 
emulsion  for  a  dozen  quarter-plates. 

Cold  Emulsijication. — This  process  is  not  very  reliable,  be- 
cause the  degree  of  sensitiveness  depends  solely,  or  to  a  great 
extent,  upon  the  temperature  of  the  air.  Henderson's  original 
process  is  as  follows  : — Allow  2  to  3  parts  of  gelatine  to  swell  in 
75  parts  of  distilled  water,  and  then  dissolve  at  a  temperature  of 
500  C.  (=112°  F.),  and  add  3  parts  of  pure  carbonate  of 
ammonia,  then  add  22  parts  of  bromide  of  ammonia  and  3  parts 
of  10  per  cent,  solution  of  iodide  of  potassium.  Finally  add  200 
parts  of  alcohol  (92  per  cent.)  and  9  parts  of  solution  of  ammonia 

143 


DICTIONARY  OF  PHOTOGRAPHY. 


(sp.  gr.  =0-91).  Dissolve  30  parts  of  nitrate  of  silver  in  150 
parts  of  water,  and  now,  in  the  dark-room,  add  the  silver 
solution  in  small  portions  and  with  frequent  shaking  to  the 
alcoholic  bromide  solution.  The  mixture  should  now  be  shaken 
frequently  for  two  hours,  the  flask  being  closed  by  means  of  a 
cork,  and  the  whole  allowed  to  stand  ten  hours,  or  if  made  in 
the  evening,  till  the  next  morning.  Forty  parts  of  Winterthur 
gelatine  must  now  be  covered  with  distilled  water,  allowed  to 
soak  for  half  an  hour,  and  then,  after  pouring  off  the  surplus 
water,  it  should  be  melted  and  added  to  the  emulsion,  which 
should  be  heated  to  350  C.  (=  950  F.).  The  whole  must  now  be 
well  shaken  and  poured  out  into  a  flat  dish  to  set  (and  this 
should  take  place  in  an  hour  or  two),  and  then  broken  up  and 
washed.  In  the  winter  it  will  be  difficult  by  this  process,  to 
obtain  a  sensitiveness  greater  than  about  150  W.  after  the 
emulsion  has  stood  ten  hours.  In  the  summer,  however,  as 
high  as  22°  W.  may  be  obtained,  but  there  is  a  danger,  if  the 
emulsion  is  allowed  to  stand  more  than  eight  hours,  of  fog 
setting  in,  or  of  obtaining  thin  emulsions  of  no  value  in  practical 
work.  Henderson's  original  method  was  to  pour  the  liquid 
emulsion  into  three  or  four  times  its  quantity  of  alcohol,  and 
stir  with  a  glass  rod  ;  when  the  emulsion  adhered  to  the  rod,  it 
was  removed,  cut  up,  and  well  washed.  Henderson  has  since 
suggested  another  process  of  making  emulsion,  which  is  some- 
what similar  to  one  proposed  by  Obernetter  in  1882.  I  give  the 
report  of  the  lecture  as  printed  in  the  British  Journal  of  Photo- 
graphy, as  some  of  the  preliminary  remarks  are  well  worth 
reading  : — 

"  Mr.  Henderson  then  proceeded  to  give  his  promised  demon- 
stration of  a  perfect  emulsion  by  a  new  method;  but,  before 
doing  so,  briefly  dealt  with  some  of  the  principal  points  in 
emulsion-making.  It  was  important,  he  said,  to  have  pure 
water  ;  he  always  experimented  with  distilled  water,  and  recom- 
mended its  use.  A  great  many  failures  were  due  to  impure 
water,  and  he  read  a  list  of  the  common  impurities  generally 
found  in  it,  and  pointed  out  that  by  employing  ordinary  water  in 
emulsion-making  certain  silver  salts  are  liable  to  be  formed  in 
the  emulsion,  which  are  not  amenable  to  some  developers,  and 
that,  therefore,  unequal  results  are  produced.  There  were 
various  way  of  making  emulsion,  and  he  enumerated  and  de- 

144 


DICTIONARY  OF  PHOTOGRAPHY.  [ElMl 

scribed  some  of  them,  among  them  the  boiling  processes,  which, 
he  considered,  produced  decomposition  of  the  gelatine,  and 
consequently  fog  in  the  image.    Incidentally,  on  the  question  of 
the  gelatine  employed,  he  remarked  that  this  substance  often 
contained  sulphurous  acid,  which  would  have  an  injurious  action 
on  the  silver  bromide.    Then  there  was  the  precipitation  pro- 
cess, in  which  no  washing  was  required,  as  well  as  his  own 
plan  of  emulsifying  with  ammonia,  for  which  the  late  Dr.  Van 
Monckhoven  had  often  been  given  credit.    He  (Mr.  Henderson) 
was  the  first  to  publish  the  method.    The  method  he  proposed 
to  show  them  that  evening  consisted  of  the  conversion  of  th<* 
silver  nitrate  into  carbonate,  and  the  introduction  of  the  latter 
into  a  solution  of  bromised  gelatine,  or  vice  versd.    Thus  the 
silver  nitrate  at  no  time  came  into  contact  with  the  gelatine.  He 
then  proceeded  to  convert  a  solution  of  silver  nitrate  into  carbon- 
ate by  means  of  a  solution  of  carbonate  of  potassium,  and, 
having  dissolved  the  gelatine  in  a  small  quantity  of  water,  added 
the  bromide  to  it,  and  mixed  the  two  solutions.    The  iodide, 
said  Mr.  Henderson,  should  be  added  after  the  bromide,  as 
iodide  of  silver  was  formed  quicker  than  the  bromide.  The 
emulsion  was  washed  by  being  forced  into  shreds  through  a 
large  mesh  into  a  sieve  placed  in  a  jar  of  water,  soluble  salts 
being  carried  off  by  a  metal  pipe.    He  condemned  the  use  of 
canvas,  and  said  less  washing  was  required  by  his  method. 
Many  failures  were  caused  by  impure  rubber  piping.  He 
recommended  the  black   kind ;   the  red  and  grey  varieties 
contain  sulphur,  which   causes  spots  in  the   emulsion.  He 
exhibited  a  small  filter  for  water  which  he  had  found  useful  and 
effective ;  it  was  a  tube  about  six  inches  long,  with  a  piece  of 
sponge  at  each  end,  and  the  centre  filled  with  charcoal.  By 
reversing  the  filter  on  the  top  it  was  self-cleansing.    Mr.  Hender- 
son filtered  his  finished  emulsion  through  wash-leather,  hastening 
the  process  by  pneumatic  pressure.    He  then  showed  a  coating 
mug,  the  emulsion  passing  through  a  piece  of  muslin  ;  he  usually 
had  a  piece  of  fine  silver  gauze.    By  this  means  he  avoided 
bubbles.    The  action  of  the  centrifrugal  separator  in  removing 
the  soluble  salts  was  then  shown.    Concluding,  Mr.  Henderson 
said  that,  if  he  wanted  an  emulsion  giving  clear  shadows  and 
great  density,  he  would  convert  the  silver  nitrate  into  acetate  or 
citrate,  instead  of  carbonate,  and  such  an  emulsion  would  do  for 

145  L 


Em  ]  DICTIONARY  OF  PHOTOGRAPHY. 

line  or  lantern  slide  work.  He  strongly  recommended  that,  in 
ripening  by  heat,  uniform  temperature  and  bulk  of  water  be 
employed.  He  further  said  that  impurities  in  chemicals  must 
be  guarded  against,  and  mentioned  the  instance  of  a  pupil  of  his 
whose  bromide,  when  tested,  was  found  to  contain  one-third  of 
another  substance,  which  the  manufacturer  subsequently  ad- 
mitted. Another  pupil  got  spotty  pictures,  which  he  (Mr. 
Henderson)  found  to  be  due  to  the  deliquescent  iodide  contain- 
ing some  sulphates.  The  formula  he  now  recommended  as  a 
good  base: — 

Silver  nitrate    120  grs. 

Water    3  ozs. 

Potassium  carbonate    60  to  90  grs. 

Water    3  ozs. 

Gelatine   240  grs. 

Potassium  bromide,...       ...       ...       ...     90  ,, 

Potassium  iodide    ...       ...        ...       ...       1  gr. 

The  gelatine  to  be  dissolved  in  sufficient  water,  and  the  emulsion 
to  be  made  up  to  fifteen  ounces.  He  preferred  to  do  without 
alcohol.  A  washed  emulsion  of  this  description,  if  treated  with 
a  solution  containing  two  grains  of  potassium  nitrate,  one  grain 
of  potassium  bromide,  and  half  a  grain  of  chrome  alum  in  ten  or 
fifteen  ounces  of  emulsion,  and  allowed  to  stand  at  a  temperature 
of  from  80  to  900  for  some  hours,  increased  in  rapidity,  and 
also  gave  more  density.  If  the  salts  are  to  be  removed  by  the 
centrifugal  separator,  it  would  be  necessary  to  have  the  bromide 
dissolved  in  a  small  quantity  of  gelatine,  say  fifteen  grains,  and 
then,  when  separation  had  taken  place,  the  bulk  of  gelatine 
added  ;  a  still  finer  precipitate  will  ensue  by  the  addition  of 
gelatine  to  the  formed  carbonate  of  silver.  In  emulsions  required 
for  subjects  of  great  contrast,  more  iodide  and  gelatine  will  be 
found  advantageous." 

There  are  several  methods  of  washing  emulsions  but  to  the 
amateur  emulsion-maker  the  simplest  is  to  place  the  set  emulsion 
in  the  piece  of  canvas  netting  previously  mentioned,  to  gather  up 
the  ends,  and  then  twist  the  same  and  force  the  emulsion  through 
the  meshes,  thus  breaking  it  up  into  little  nodules,  or  shreds, 
which,  presenting  a  greater  surface  to  the  washing  water,  allow  of 

146 


DICTIONARY  OF  PHOTOGRAPHY.  [EmU 

a  quicker  extraction  of  the  inert  salts.  The  squeezing  of  the 
emulsion  should  always  be  done  in  distilled  water,  care  being 
taken  to  wash  both  the  hands  and  canvas  well  first,  and  rinsing 
the  same  in  distilled  water.  In  breaking  up  the  emulsion  in  this 
way  there  is  always  some  lost  by  adherence  to  the  canvas,  but 
not  much  ;  and  where  experimental  batches  of,  say,  4  or  5  ounces 
only  are  made,  the  simplest  plan  is  to  cut  the  emulsion  up,  with 
a  silver  fruit-knife,  into  little  dice,  and  then  place  these  in  a 
beaker  of  distilled  water,  stirring  frequently  during  the  course  of 
an  hour.  If,  however,  it  is  inconvenient  to  give  so  much  time  to 
it,  the  simpler  way  is  to  collect  all  the  dice  on  a  piece  of  well- 
washed  calico,  gather  up  the  loose  ends  and  tie  them  together,  and 
suspend  the  little  bag  thus  made  by  the  aid  of  a  piece  of  string 
on  to  a  glass  rod ;  place  this  across  the  mouth  of  a  decent- 
sized  beaker  or  jar,  fill  the  jar  sufficiently  full  with  distilled 
water  to  cover  the  bag,  and  leave  it  for  an  hour  or  two.  The 
water  filling  the  bag  extracts  the  useless  nitrates  and  excess  of 
bromides,  and  being  heavier  than  the  pure  water  sinks  to  the 
bottom  of  the  vessel,  so  that  there  is  always  a  current  of  water 
less  heavily  charged,  and  the  washing  is  mechanically  performed. 
After  about  two  hours  of  this  soaking,  the  water  should  be 
changed,  the  bag  being  allowed  to  drain  well  before  the  vessel  is 
refilled.  Washing  may  thus  be  effected  very  thoroughly  in  from 
six  to  eight  hours,  or  comfortably  in  a  day.  Twenty-four  hours 
is  not  actually  too  much — in  fact,  very  strongly  recommended  by 
Eder  and  other  authorities.  If  a  good  supply  of  water  is  to  be 
had,. the  washing  may  be  performed  by  fixing  the  vessel  under  a 
tap,  and  allowing  the  same  to  run  on  it  all  night,  but  personally 
I  think  it  is  better  to  use  distilled  water  even  for  washing  the 
emulsion.  There  is  one  method  of  washing  the  emulsion  which 
is,  I  believe,  rarely  used  by  commercial  makers,  and  that  is  by  the 
aid  of  alcohol,  as  was  noted  in  speaking  of  Henderson's  emulsion 
process.  As  soon  as  the  cooking  is  finished,  the  still  warm  and 
liquid  emulsion  is  poured  into  three  or  four  times  its  quantity  of 
alcohol,  and  well  stirred  round.  The  extraction  of  the  unneces- 
sary salts  is  not  so  complete  and  is  more  costly  than  when  washing 
is  effected  with  water,  but  it  is  of  advantage  in  saving  time  and 
there  is  less  chance  of  frilling  in  the  subsequent  operations  of 
developing,  etc.  After  washing  by  this  method,  it  is  essential  to 
allow  the  emulsion  to  soak  in  water  for  an  hour,  in  order  that  it 

147 


Emu] 


DICTIONARY  OF  PHOTOGRAPHY. 


may  absorb  the  necessary  amount  of  water.    When  the  emulsion 
has  been  sufficiently  washed,  it  should  be  collected  on  a  piece  of 
clean  and  well-washed  linen,  allowed  to  drain,  and  gently  squeezed 
so  as  to  press  out  the  superfluous  water,  then  collected  and 
melted  by  placing  it  in  a  beaker  or  other  convenient  vessel, 
which  should  be  placed  in  a  water  bath.    Care  should  be  taken 
not  to  heat  the  emulsion  too  much,  or  else  it  will  become  fogged, 
and  useless,  and  the  more  rapid  the  emulsion  the  less  heat  it  will 
bear  in  this  second  melting.    However  careful  has  been  one's 
method  of  preparation  and  washing,  one  is  never  certain  that  the 
emulsion  is  free  from  mechanical  impurities,  such  as  little  bits  of 
fibre,  hair,  etc.,  and  it  is  therefore  advisable  to  filter  the  emulsion 
before  use.    For  this  purpose,  flannel,  felt,  or  wash-leather  may 
be  used,  and  whilst  the  flannel  is  the  quickest  to  allow  the 
emulsion  to  pass,  leather  is  the  most  effectual.    Personally,  I 
always  use  a  felt  filtering  bag,  such  as  may  be  obtained  from  any 
chemist  to  order,  z  bout  2s.  for  a  pint  size,  which  will  be  too  large 
for  most  amateur  workers,  as  the  bag  absorbs  too  much  emulsion, 
but  the  bag  may  easily  be  cut  down  to  half  its  size.     If  wash- 
leather  be  used,  it  is  necessary  to  wash  it  well  in  weak  soda 
solution  first,  about  I  in  20,  to  free  it  from  the  natural  grease, 
and  then  wash  thoroughly  to  free  from  the  soda.    When  the 
emulsion  is  perfectly  fluid,  it  should  be  poured  into  the  bag, 
presuming  the  felt  bag  be  used,  or  into  the  wash-leather  or 
flannel  stretched  on  a  filter.    When  the  felt  bag  is  used,  it  is  only 
necessary  to  suspend  it  by  its  ring  from  a  retort  stand,  or  any 
convenient  makeshift,  and  thus  less  emulsion  is  lost,  and  it  does 
not  get  cold  quite  so  quickly.    Gentle  pressure  on  the  top  of  the 
bag  soon  forces  the  emulsion  through.    With  wash-leather  it  is 
almost  necessary  to  have  some  pumping  arrangement,  and  this 
may  be  either  the  ordinary  indiarubber  balls  as  used  for  spray 
diffusers,  or  the  more  powerful  brass  force  pump  used  for  filling 
pneumatic  cycle  tyres  or  footballs.    When  leather  or  flannel  is 
used,  the  most  convenient  filtering  apparatus  I  have  found  to  be 
a  small  glass  percolator,  a  utensil  known  to  every  chemist,  and 
this  fitted  with  a  cork  to  the  upper  part  or  body  allows  one  to 
affix  the  forcing  arrangement.    It  is  advisable  before  using  the 
emulsion  for  coating,  to  add  some  bromide,  and  a  little  chrome 
alum  to  the  emulsion,  the  latter  especially  when  the  process 
adopted  has  been  the  ammonia  boiling  process,  as  this  addition 

148 


DICTIONARY  OF  PHOTOGRAPHY.  [EmU 

prevents  fog  and  frilling.  A  I  per  cent,  solution  of  bromide  of 
ammonium,  and  a  2  per  cent,  solution  of  chrome  alum  should  be 
made,  and  1  oz.  of  each  should  be  added  to  every  pint  of  emul- 
sion. The  addition  of  chrome  alum  lowers  the  sensitiveness 
slightly  ;  at  least,  so  it  is  said,  and  certainly  I  think  it  does,  but 
there  are  no  ill  effects  if  the  chrome  alum  be  rendered  neutral  by 
the  cautious  drop  by  drop  addition  of  solution  of  ammonia.  The 
addition  of  the  chrome-alum  solution  should  be  made  to  the 
emulsion  very  gradually,  with  shaking  between  each  addition, 
and  this  addition  may  be  made  either  before  or  after  filtration, 
preferably  after.  Many  workers  add  a  little  alcohol  to  the  emul- 
sion, to  make  it  flow  over  the  plates  ;  and  it  is,  I  think,  to  be 
recommended  when  coating  is  to  be  done  by  hand.  One  part  of 
pure  rectified  spirit  of  wine  to  every  twenty  parts  of  emulsion  is 
the  right  proportion.  The  necessary  utensils  for  coating  plates 
may  be  either  very  simple,  or  more  or  less  elaborate,  according 
to  the  operator's  ideas.  The  one  absolute  essential  is  a  levelling 
stand,  and  if  we  are  going  to  coat  any  quantity  of  plates,  a  good- 
sized  sheet  of  plate  glass  and  a  level.  All  these  may  be  bought 
from  any  photographic  dealer,  or  the  glass  alone  obtained  from 
any  glass  warehouse.  Sheets  of  glass  of  the  necessary  size,  we 
need  not  say,  are  also  essential.  The  glass  on  which  the  emul- 
sion is  to  be  spread  should  be  well  cleaned,  and  for  this  purpose 
tripoli  made  into  a  paste  with  methylated  spirit  may  be  used,  or 
prepared  chalk  made  into  a  thin  cream  with  water.  After  rub- 
bing the  glass  well  with  either,  it  should  be  rinsed  in  tepid  water, 
then  well  rinsed  again  in  hotter  water,  and  given  a  final  rinse  in 
hot  water,  when  it  may  be  placed  in  a  rack  to  drain,  and,  if 
thought  necessary,  polished  with  a  soft  wash-leather,  which  has 
been  freed  from  grease  by  washing  in  soda.  When  the  glass  is 
cleaned,  each  piece  should  he  taken  up  by  means  of  a  pneumatic 
holder,  which  may  be  obtained  from  any  photographic  warehouse, 
and  examined  for  flaws  and  large  bubbles  ;  all  defective  pieces 
being  rejected.  The  glass  should  be  piled  together  and  heated 
by  being  placed  in  an  oven  or  before  the  fire  for  a  little  time.  It 
must  not,  however,  be  made  too  hot,  only  just  pleasantly  warm, 
so  as  not  to  chill  the  emulsion  when  it  is  poured  on.  A  measure 
may  also  be  used  by  the  amateur  in  his  first  trials  to  measure 
out  the  quantity  of  emulsion,  but  with  a  little  practice  one  is  soon 
accustomed  to  pouring  out  about  the  right  quantity.    The  method 

149 


Emu]  DICTIONARY  OF  PHOTOGRAPHY. 


of  coating  depends  upon  the  size  of  plate ;  with  small  plates — 
for  instance,  half  and  quarter  plates — it  may  be  poured  into  the 
middle  of  the  plate,  which  is  supported  by  the  pneumatic  holder, 
and  then  the  emulsion  made  to  run  to  the  four  corners  by  tilting 
the  plate  as  when  coating  a  plate  with  collodion.  This,  however 
is  not  a  very  easy  matter,  and  it  is  far  simpler  to  pour  the  emul- 
sion in  a  line  right  across  the  plate,  and  spread  by  means  of  the 
simple  little  distributor  shown  in  fig.  29,  which  is  a  piece  of 
glass  rod,  not  tubing,  bent  to  the  above  shape  in  a  Bunsen  flame  ; 
this  is  placed  in  hot  water  till  quite  hot,  wiped  dry,  and  then  the 
emulsion  is  spread  with  it,  the  plate  being  on  the  plate  of  glass 
on  the  levelling  stand.  Mr.  W.  K.  Burton,  in  his  well-known  and 
excellent  little  handbook  11  Modern  Photography,"  describes  a 
different  method  of  coating,  which  I  have  used  with  success,  and 
as  I  have  also  one  of  the  drying  boxes  he  describes,  I  give  the 
extract  from  the  book  entire. 

"  There  are  several  methods  of  coating  plates  in  common  use. 
The  best  for  those  who  have  the  skill  is  the  method  used  for 
coating  with  collodion,  and  which  we  describe ;  but  we  imagine 
most  of  those  who  have  not  worked  the  wet  process  will  find  the 
plan  which  has  been  used  for  some  time  by  the  writer,  and  which 
is  also  described,  the  most  convenient.  For  the  ordinary  method 
the  apparatus  necessary  is  as  follows  : — 

"  A  small  teapot.  A  large  flat  dish  of  the  nature  of  a  porcelain 
flat  bath  to  catch  spillings.  A  pneumatic  holder.  This  is  an 
india-rubber  ball  with  sucker  attached,  the  whole  forming  an 
apparatus  whereby  it  is  possible  to  pick  up  a  plate. 

"  In  coating  by  the  ordinary  method,  it  is  advisable  to  have 
two  ruby  lamps,  one  placed  at  the  back  of  the  operating  table  f 
the  other  in  front  of  the  operator,  and  above  the  level  of  his 
head.  He  can  thus  see  the  emulsion  on  the  plate,  both  by  re- 
flected and  by  transmitted  light.  The  flat  dish  is  placed  between 
the  lower  light  and  the  operator ;  the  teapot  full  of  emulsion, 
melted,  and  at  a  temperature  of  1200  F.,  or  thereby,  may  be 
placed  on  this  dish,  and  the  plates,  polished  side  downwards,  are 
placed  to  the  right  of  the  flat  dish. 

"The  pneumatic  holder  is  taken  in  the  left  hand,  which  is 
stretched  across  the  flat  dish,  to  take  hold  of  a  plate.  The  plate 
is  held  level,  and  a  pool  of  emulsion  is  poured  on  to  it,  and 
guided  over  it  exactly  as  was  described  for  varnishing  a  plate. 

150 


DICTIONARY  OF  PHOTOGRAPHY. 


[Emu 


The  only  difference  is  that  more  than  half  the  plate  is  at  first 
covered  with  emulsion,  and  that,  instead  of  the  plate  being 
drained,  it  is  only  slightly  tipped  up,  so  as  to  let  a  little  of  the 
emulsion  return  to  the  teapot.  After  this  is  done,  the  plate  is 
gently  rocked  for  a  few  seconds,  till  we  see  by  looking  through 
it  that  the  coating  has  spread  evenly.  To  tell  whether  the 
plate  has  had  enough  emulsion  left  on  it,  we  look  through  it. 


Fig.  28. 


after  it  has  set,  at  one  of  the  ruby  lights.  If  we  can  see  the 
form  of  the  light  through  the  film,  there  is  not  enough  emulsion 
on  the  plate. 

"The  plates,  as  they  are  coated,  are  placed  on  the  levelling 
slab  to  set.  Some  emulsion  is  sure  to  be  spilled  into  the  flat 
dish.  It  is  allowed  to  set,  is  then  scraped  up  with  a  strip 
of  glass,  and  remelted.    For  the  method  of  coating  which  we 


Fig.  29. 


recommend  to  those  not  skilled  in  the  wet  process  the  pneumatic 
holder  is  not  required.  It  is  necessary,  however,  to  make  a  small 
tripod.  This  is  done  by  gluing  three  somewhat  large-sized  shot  on 
to  a  quarter-plate  in  the  form  of  a  triangle,  (see  fig.  28). 

"  There  is  also  needed  a  glass  rod  about  two  inches  longer 
than  the  width  of  the  plate  to  be  coated,  and  a  jam  pot  or  glass 
measure  in  which  to  stand  the  rod.  The  dark-room  lamp  is 
placed  within  a  few  inches  of  the  left-hand  end  of  the  levelling 

151 


EmuJ  DICTIONARY  OF  PHOTOGRAPHY. 

shelf,  and  to  the  back  of  it.  There  is  to  the  left  of  the  lamp 
room  only  for  the  pile  of  plates,  which  in  this  case  have  the 
polished  side  upwards.  The  rod  standing  in  the  jam-pot  is  to 
the  right  of  the  lamp.  The  teapot  with  emulsion  in  it,  as  before, 
is  in  front  of  the  lamp,  and  farther  forward  still,  near  the  front 
edge  of  the  slab,  is  the  small  tripod  mentioned.  A  plate  is  taken 
from  the  pile,  and  placed  on  the  tripod. 

"  A  pool  of  emulsion,  about  half  covering  the  plate,  is  poured 
from  the  teapot.  The  glass  rod  is  taken  between  the  fingers 
and  the  thumb  of  each  hand,  and  dipped  into  the  pool  of  emulsion 
right  across  the  plate.  The  emulsion  will  run  between  the  rod 
and  the  plate  to  each  edge  of  the  latter.    By  a  motion  of  the 


Fig.  30. 


finger  and  thumb  of  each  hand,  the  rod  is  lifted  the  smallest 
possible  distance  from  the  plate,  and  is  rapidly  moved  first  to 
one  end,  then  to  the  other,  the  tips  of  the  finger  and  thumb 
resting  on  the  level  table  as  a  guide.  This,  if  properly  done, 
will  cover  the  whole  plate  with  emulsion ;  and  if  the  plate  be 
small — half-plate  or  under — it  is  sufficient  to  send  it  to  the  far 
end  of  the  table  to  set.  If  the  plate  be  large,  the  coating  will 
not  be  evenly  spread  unless  it  is  lifted,  balanced  on  the  tips 
of  the  fingers  of  the  left  hand,  and  rocked  gently  for  a  few 
seconds.  By  this  method  the  plates  may,  after  a  little  practice 
be  coated  with  great  rapidity.  There  is  no  need  to  wipe  the  rod 
each  time  it  is  used. 

"As  no  excess  is  poured  off  the  plate  nor  spilled  in  this 
method,  it  is  possible,  by  using  a  very  small  teapot,  to  keep  a 

I52 


DICTIONARY  OF  PHOTOGRAPHY. 


[Emu 


constant  check  on  the  quantity  of  emulsion  going  on  to  the 
plates.  The  covering  power  of  the  slow  emulsion  will  be  found 
somewhat  greater  than  that  of  the  rapid.  With  each  ounce  of 
the  slow  emulsion,  eight  quarters  or  four  half-plates  may  be 
coated  ;  with  the  rapid,  only  seven  quarters  or  three 
halves. 

"The  plates  will  'set'  in  a  few  minutes — that  is 
to  say,  the  emulsion  will  stiffen  like  a  jelly,  and  will 
not  run  off  the  glass,  whatever  position  it  is  placed 
in.  They  are  now  transferred  to  the  drying  box. 
When  dry,  they  are  ready  for  use. 

"The  drying  box  calls  for  some  description.  There 
are  various  forms  in  use.  They 
all  have  in  view  the  inducing  of 
a  current  of  air  among  the  plates 
generally  by  the  burning  of  a  gas 
jet  in  a  tube  or  chimney.  The 
fault  of  most  is  that  the  air 
passages  are  far  too  contracted. 
In  many,  heat  is  applied  to  the 
incoming  air.  This  is  quite  un- 
necessary if  the  air  passages  are 
sufficiently  large  and  well  arranged, 
and  if  the  box  can  be  placed  in  a 
fairly  dry  place.  It  is,  moreover, 
the  greatest  mistake  to  use  artificial 
heat  in  drying  plates,  if  it  can 
possibly  be  avoided,  as  they  are 
rendered  distinctly  slower  thereby. 

"  We  illustrate  (fig.  3 1 )  a  form  .  0 

of  box  which  has  been  in  use 

by  the  writer  for  several  years,  and  has  given  complete  satis- 
faction. It  will  be  seen  that  the  air  enters  at  the  top  of  the  box. 
It  is  drawn  into  an  air  chamber  at  its  lower  portions,  and  hence 
passes  up  the  large  tube  with  a  gas  flame  burning  in  it.  This 
tube  must  be  carried  either  into  the  open  air  or  into  a  chimney. 
The  plates  are  placed  in  racks,  which  were  first  designed  by 
Mr.  G.  F.  Williams.  A  sketch  of  one  of  these  is  given  (fig.  30). 
Two  plates  may  be  placed  back  to  back  in  each  pair  of  notches 
if  desired.    The  racks  may  be  placed  on  the  cross  rods  shown 

153 


Ena]  djictionary  op  photography. 

in  the  box,  the  height  of  which  may  be  adjusted  to  suit  various- 
sized  plates.  Boxes  and  racks  as  described  are  made  by  Messrs. 
D.  Gordon  Laing  &  Son,  2,  Duke  Street,  Adelphi,  London,  W.C." 
As  an  alternative  method  of  drying  plates,  the  following  may  be 
adopted,  and  it  is  one  which  personally  I  prefer  to  that  suggested 
by  Mr.  Burton.  All  that  is  required  is  an  air-tight  box  and  some 
anhydrous  calcium  chloride.  The  plates  to  be  dried  should  be 
merely  placed  in  racks  in  the  box,  and  a  porcelain  dish,  as  large 
as  the  box  will  hold,  in  the  bottom.  In  the  dish  place  the 
anhydrous  chloride  of  calcium,  put  the  dish  in  the  box,  the  racks 
containing  the  plates,  and  shut  the  door,  or  lid,  and  leave  for 
three  days,  by  which  time  the  plates  should  be  perfectly  dry.  In 
no  case  should  the  box  be  opened  till  a  reasonable  time  has 
elapsed,  or  else  peculiar  markings  will  be  caused,  due  to  unequal 
drying.  When  the  calcium  choride  has  once  been  used,  it  should 
be  heated  in  an  oven  till  it  fuses  and  melts,  when  it  will  lose 
all  the  water  it  has  absorbed.  The  disadvantage  of  drying 
by  air  alone  is  that  the  rate  of  drying  is  proportionate  to  the 
amount  of  moisture  in  the  air,  and  that  the  unequal  drying 
caused  by  a  fall  in  temperature  may  give  rise  to  marks  which 
are  absolutely  irremovable  and  always  show  in  the  finished 
negative. 

Enamels  are  photographic  images  burnt  into  porcelain  and 
coated  with  a  porcelain  glaze,  which  makes  them  absolutely  per- 
manent. They  are  usually  prepared  on  small  copper  plaques, 
which  are  coated  with  a  special  porcelain  or  material,  which  may 
practically  be  considered  to  be  glass.  Metal  plaques  already  pre- 
pared can  be  obtained  commercially.  On  these  an  image  is  laid 
and  fired.  There  are  several  processes — (a)  the  substitution 
process,  (b)  the  powder  process,  (c)  the  pigment  or  carbon  pro- 
cess, (d)  the  collotype  process.  For  the  substitution  process  a 
collodio-chloride  printed-out  positive  is  prepared,  toned,  and 
fixed.  The  image  is  toned  with  platinum,  gold,  palladium, 
iridium,  manganese,  and  uranium.  The  positive  is  then  stripped, 
transferred  to  the  plaque,  and  carefully  smoothed  out,  and  then 
fired,  coated  with  glaze,  and  refired.  The  powder  process  is  the 
preparation  of  a  positive  by  the  powder  or  dusting-on  process  on 
a  sheet  of  glass,  coating  it  with  collodion,  stripping,  and  transfer- 
ring to  the  plaque,  and  firing.    The  pigment  process  is  merely  a 

154 


DICTIONARY  OF  PHOTOGRAPHY.  [EllC 

modification  of  the  carbon  process,  gum  arabic  instead  of  gelatine 
being  used  as  the  material;  it  is  transferred  and  fired.  The 
collotype  process  is  used  for  preparing  the  image,  a  special  ink 
being  used  and  the  print  being  on  litho-transfer  paper,  from 
which  it  is  transferred  to  the  plaque.  It  is  impossible  to  enter 
fully  into  the  subject,  and  the  process  is  one  very  little  used  at 
the  present  day. 

Enamelling  Prints.  This  consists  of  coating  the  finished 
print  with  a  film  of  collodion  to  give  it  a  brilliant  surface,  which 
gives  greater  protection  and  more  softness  and  depth.  The 
following  is  the  method  of  procedure : — Clean  a  glass  plate — 
an  old  negative  glass  or  a  cutting  shape  will  do — with  French 
chalk,  and  polish  thoroughly  ;  now  coat  the  plate  with  enamel 
collodion  (see  Collodion),  and,  having  made  a  solution  of 
gelatine,  10  grs.  to  the  ounce  of  distilled  water,  slip  the 
collodionised  plate  and  the  print  carefully  into  the  solution  of 
gelatine,  avoiding  air  bubbles  ;  bring  the  print  face  downwards 
into  contact  with  the  coated  plate,  remove  from  the  solution, 
and  squeeze  into  optical  contact,  and  allow  to  dry.  When 
thoroughly  dry,  raise  one  corner  with  a  knife,  and  the 
print  will  strip  from  the  glass,  bearing  the  collodion  film 
with  it. 

Encaustic  Paste.  A  paste  used  to  give  a  brilliant  surface 
to  the  finished  print  without  the  use  of  hot  rollers  or  of  collodion. 
There  are  several  formulae ;  but  the  following,  proposed  by 
Salomons,  is  decidedly  the  best : — 

Pure  white  wax    500  grs.    or  32  grms. 

Gum  elemi    10  -6  grm. 

Benzole    4  drms. ,,    14  c.cm. 

Essence  of  lavender   6     ,,     ,,    21  ,, 

Oil  of  spike    1  drm.  ,,  3-5  ,, 

Melt  the. wax  and  elemi,  add  the  benzole  and  other  ingredients, 
and  allow  to  cool,  stirring  frequently.  Smear  a  little  of  the  paste 
over  the  face  of  the  print  with  a  tuft  of  cotton-wool,  and  polish 
with  a  clean  piece  till  the  surface  is  clean  from  markings.  It 
increases  the  depth  of  shadow  and  general  beauty  to  a  large 
extent.    A  more  simple  paste  can  be  made  as  follows  : — 

155 


End] 


DICTIONARY  OF  PHOTOGRAPHY. 


Dr.  Eder's  Cerate  Paste. 


Pure  white  wax 
Dammar  varnish 
Pure  oil  of  turpentine 


...  100  grs.  or  6-5  grms. 
...  40  mins.  „  2*5  can. 
...  100    „      „     6  „ 


Prepared  and  used  as  above  described. 

Endemann's  Process.   See  Aniline  Process. 

Enlarging  is  the  operation  of  obtaining  a  larger  image  of 
a  negative  or  positive  upon  some  sensitive  surface.  There  are 
several  methods  of  doing  this,  either  by  the  use  of  daylight  or 
artificial  light,  which  will  be  severally  described.  But  it  is  first 
necessary  to  make  a  few  remarks  upon  the  negative  used  for 
this  purpose.  Absolute  sharpness  of  focus  is  a  sine  qua  non  ; 
for,  supposing  a  quarter-plate  negative  taken  in  the  ordinary  way 
is  to  be  enlarged — it  may  be  considered  that  the  discs  of  confusion 
appear  as  points  of  less  than  Ti„  of  an  inch  in  diameter,  a  point 
inappreciable  to  the  human  eye  ;  but  if  these  said  discs  of  con- 
fusion are  enlarged,  they  will  become  of  appreciable  size — viz., 
enlarge  a  quarter-plate  to  12  by  10,  or  three  times,  and  these 
discs  of  confusion  will  be  enlarged  in  the  same  ratio ;  therefore 
they  will  be  about  Tf  of  an  inch  in  diameter,  and  will  be  easily 
seen.  Again,  the  negative  should  be  plucky,  and  with  good,  but 
not  too  great,  contrasts,  and  of  accurate  density ;  in  fact,  a  good 
silver  printing  negative  will  give  a  good  enlargement.  For  con- 
venience sake  we  may  divide  our  apparatus  into  two  classes  ; 
first,  that  required  for  daylight  enlarging ;  and,  secondly,  that 
required  for  artificial  light.  We  may  again  subdivide  our  two 
classes  into  minor  sub-classes  :  thus,  daylight  enlarging  may  in- 
clude (1)  Solar  work,  (2)  Diffused  light;  and  artificial  light 
includes  (1)  Lantern  work,  including  the  use  of  condensers; 
(2)  Work  without  condensers.  Then,  again,  we  may  use  petro- 
leum, gas,  enriched  gas,  limelight,  or  magnesium  these,  however, 
will  be  described  as  we  go  on. 


(1)  Solar  Work.  By  this  term  we  understand  the  use  of  the 
solar  rays  themselves,  and  not  their  light  reflected  from  any  card 
or  white  surface.  Although  this  was  one  of  the  first  processes 
employed  before  bromide  paper  was  invented,  and  was  used  for 


Daylight  Enlarging. 


156 


DICTIONARY  OF  PHOTOGRAPHY.  [Enl 


printing  on  ordinary  silver  paper,  carbon  tissue,  etc.,  we  shall 
dismiss  this  in  a  few  words,  because  the  apparatus  is  costly,  and 
sunlight,  unfortunately,  not  always  to  be  turned  on  and  off  at 
will.  For  this  work  Woodward  invented  his  solar  camera,  and 
Monckhoven  improved  upon  this  with  his  dialytic  apparatus, 
other  instruments  also  being  made  for  the  same  purpose.  Large 
condensers  are  absolutely  necessary,  not  less  than  nine  inches  in 
diameter,  and  the  solar  rays  have  either  to  be  kept  motionless  by 
means  of  a  heliostat,  or  mirror  mounted  equatorially  and  driven 
by  clockwork,  or  else  by  careful  and  attentive  work  of  an 
operator.  As,  however,  equally  good  results  can  be  obtained  by 
using  the  apparatus  described  hereafter,  no  further  description 
will  be  given  ;  but,  for  the  information  of  those  desirous  of 
spending  their  money,  full  and  complete  instructions  will  be 
found  in  Monckhoven's  "  Optics." 

(2)  Enlarging  by  Diffused  Daylight.  By  many  this  will  be 
found  the  most  convenient  and  cheapest  method  of  making 
enlargements  ;  but  as  to  whether  it  is  the  best  is  altogether 
another  question,  which  we  shall  consider  later  on  at  the  end  of 
the  instructions  for  both  methods  of  illumination.  We  have  here 
also  what  may  be  practically  considered  as  two  distinct  methods 
of  working,  the  one  using  the  actual  light  of  the  sky  itself,  and 
the. other  using  reflected  skylight.  Before  entering  into  particulars 
of  either  method,  however,  there  are  one  or  two  details  which  it 
is  advisable  to  elucidate.  We  may  decide  to  use  a  darkened 
room  or  a  special  camera  for  the  purpose  of  obtaining  the 
enlargement,  and  the  necessary  arrangements  will  now  be 
described.  If  we  desire  to  use  a  darkened  room,  such  as  an 
ordinary  sitting-room,  it  is  obviously  necessary  that  the  light 
shall  be  prevented  from  having  access  to  it  by  some  means  or 
other ;  therefore  we  will  suppose  that  the  room  has  one  window, 
which,  if  possible,  should  face  the  north,  and  it  is  desired  to 
block  out  this  window  temporarily,  so  that  the  room  may  be 
afterwards  used  in  the  ordinary  way.  It  is  obvious  that  pasting 
brown  or  non-actinic  paper  on  the  panes  of  glass  is  not 
admissible ;  therefore  we  must  have  recourse  to  some  other 
arrangement  which  can  be  temporarily  applied  and  bodily  re- 
moved when  done  with.  A  convenient  contrivance,  which  can 
be  very  cheaply  put  together  by  any  one  possessing  a  little 
knowledge  of  carpentering,  may  be  made,  or  any  working  carpenter 

*57 


Enl] 


DICTIONARY  OF  PHOTOGRAPHY. 


will  knock  it  up  in  a  few  hours  at  a  trifling  charge.  To  make 
it  still  plainer  we  will  take  an  actual  example  made  for  our  own 
use.  The  window  which  it  was  requisite  to  block  up  measured 
six  feet  by  four  feet,  and,  like  most  windows,  was  divided  across 
the  middle  by  a  double  sash.  The  sashes  of  the  window 
measured  at  the  sides  one  inch  in  breadth  ;  at  the  top  and 


Fig.  S2. 

bottom,  two  inches.  Two  frames  were  therefore  made,  one  to 
fit  into  the  upper  part  of  the  window,  and  one  into  the  lower ; 
the  upper  frame  is  shown  in  fig.  32,  the  lower  in  fig.  33.  The 
frames  were  made  of  deal  half  an  inch  thick  and  two  inches 
wide :  the  upper  one,  fig.  32,  had  a  crosspiece  to  strengthen  it, 
which  was  also  convenient  to  lift  it  up  by ;  the  lower  one,  fig.  33, 
had  two  crossbars  to  strengthen  it,  and  which  were  also  used,  as 
described  hereafter,  for  the  reception  of  the  negative.    We  have 

158 


DICTIONARY  OF  PHOTOGRAPHY. 


[Enl 


now  the  skeleton,  and  it  is  only  necessary  to  clothe  it  to  make  it 
a  complete  and  useful  piece  of  apparatus.  For  this  purpose 
stout,  dark-brown  American  cloth,  which  is  a  kind  of  coarse 
canvas  covered  with  some  coloured  water-proof  substance,  was 
chosen,  and  this  was  tacked  on  to  the  upper  frame,  and  the 
edges  brought  round  to  the  back  of  the  frame  so  as  to  exclude 


Fig.  33- 


any  stray  ray  of  light  which  might  otherwise  creep  in  ;  the  shiny 
side  of  the  cloth  was  at  the  back,  the  woolly  side  being  towards 
the  window.  To  make  absolutely  certain  that  no  light  penetrated 
the  cloth,  ruby  paper  was  pasted  on  the  woolly  side  of  the  cloth. 
At  the  edges  of  the  frame,  where  it  touched  the  sashes  of  the 
window,  a  double  thickness  of  woollen  list  was  tacked  ;  so  that, 
when  the  frame  was  inserted  in  place  and  secured  at  the  top  by 
a  turn  button  and  at  the  bottom  by  the  catch  of  the  window, 

iS9 


Enl] 


DICTIONARY  OF  PHOTOGRAPHY. 


there  was  sufficient  pressure  on  the  frame  to  make  it  fit  up  close 
to  the  sash  and  exclude  all  light.  The  lower  frame  was  treated 
in  the  same  way,  with  this  exception,  that  an  aperture  was  cut  in 
the  cloth,  and  the  edges  then  nailed  to  the  little  crosspieces, 
where  the  negative  is  afterwards  placed ;  when  these  two  frames 
are  fitted  into  the  window  and  the 
aperture  blocked  up,  there  should  be 
no  stray  streaks  of  light  anywhere. 
Brown  paper,  of  course,  may  be  used 
instead  of  American  cloth,  but  the 
latter  is  much  more  durable,  and  less 
likely  to  suffer  accidental  damage  by 
the  fingers  being  put  through  it.  Now, 
let  us  see  as  to  using  a  special  camera, 
so  that  we  may  not  need  to  darken 
the  room.  To  make  a  camera  which 
shall  answer  this  purpose  is  evidently 
not  very  difficult,  and  we  will  give  an 
idea  on  the  subject  and  leave  ou 
readers  to  work 
out  the  details 
themselves.  The 
operator's  own 
camera  and  lens 
may  be 
used,  and  a 
makeshift 
arrange- 
ment con- 
sisting of 

black  silesia  running  on  iron  rods,  and  fitting  on  to  the  lens  at 
one  end,  and  bearing  a  focussing  screen  and  a  dark  slide  to  hold 
the  sensitive  surface  at  the  other.  We  have  seen  earlier  that 
we  may  use  the  actual  light  of  the  sky  itself,  and  this  is  shown 
also  in  fig.  34,  where  the  camera  is  presented  to  the  sky.  If  we 
are  using  a  darkened  room,  then  the  camera  must  be  tilted  in  the 
same  manner;  this  may  have  some  advantages,  which  in  our 
opinion  are  outweighed  by  the  extremely  awkward  manner  in 
which  the  camera  has  to  be  sloped,  the  sensitive  surface,  of 
course,  having  to  be  parallel  with  the  negative.    We  come  back, 

160 


DICTIONARY  OF  PHOTOGRAPHY. 


Enl]  DICTIONARY  OF  PHOTOGRAPHY. 

therefore,  to  the  method  of  using  the  reflected  skylight,  and 
fig.  35  will  show  us  how  to  arrange  the  whole  apparatus.  We 
have  described  the  method  of  blocking-out  the  window.  The 
method  of  placing  the  negative  in  position,  if  more  than  one  size 
is  to  be  enlarged  from,  is  by  the  use  of  carriers  as  used  in  dark 
slides,  which  should  be  provided  with  little  buttons  for  fastening 
in  place,  and  springs  for  holding  the  negative,  these  said  carriers 
fitting  into  the  aperture  in  the  window.  Or  the  negative  may  be 
placed  in  the  dark  slide  of  the  camera,  and  the  slide  inserted  in 
the  groove  in  the  ordinary  way,  and  the  shutters  of  the  slide 
pulled  out  so  as  to  allow  of  the  free  passage  of  the  light  through 
the  negative.  The  camera  must  be  pushed  close  up  to  the 
negative,  or  a  cloth  so  arranged  that  no  light  enters  the  room 
but  that  transmitted  through  the  negative.  It  is  not,  of  course, 
absolutely  necessary  that  the  camera  should  be  used  actually. 
All  that  is  necessary  is  a  board  to  support  the  lens,  the 
focussing  cloth  or  a  black  sleeve  to  prevent  all  light  but  that 
transmitted  through  the  negative  from  having  access  to  the 
sensitive  surface.  It  will  be  found  convenient  if  the  camera  or 
the  lens  and  easel  or  board  for  the  support  of  the  sensitive 
surface  be  on  the  same  level,  so  that  a  board  or  table  may  be 
used,  as  seen  in  fig.  35,  to  obtain  this  end.  The  table  or  board 
should  have  two  parallel  pieces  of  wood  nailed  to  it,  so  as  to 
enable  the  camera  and  sensitive  surface  to  be  kept  exactly 
parallel.  The  next  question  is  the  reflector  (see  fig.  35)  outside 
the  window.  Many  operators  use  a  mirror  for  this  purpose,  but 
the  objection  to  this  is  that  a  dark  and  a  white  cloud  passing 
simultaneously  over  it,  or  actually  the  image  of  the  clouds,  will 
cause  unequal  illumination  of  the  negative,  and  consequently 
unequal  illumination  of  the  enlargement.  Certainly  a  mirror 
gives  the  greatest  illumination.  In  place  of  the  mirror,  a  sheet 
of  white  cardboard,  enamelled  iron,  or  opal  glass  may  be 
used.  The  operator  will  make  his  own  choice  in  this  matter. 
The  reflector  must  be  fitted  at  an  angle  of  45°  outside  the 
window ;  and  a  cord  fastened  to  the  top  of  it,  and  passing 
through  the  sash  at  the  middle  of  the  window,  will  keep  it  in 
position,  and  enable  it  to  be  raised  or  lowered  at  will.  We  use 
a  sheet  of  opal  glass  mounted  in  an  old  picture  frame,  which  is 
hinged  at  the  lower  end  to  the  bottom  of  the  window  sash,  and 
fastened  by  a  cord  at  the  top  to  the  middle  of  the  sash ;  a  gimlet 

16? 


DICTIONARY  OF  PHOTOGRAPHY.  [Elil 

was  used  to  make  a  hole  in  the  sash,  and  the  cord  run  through 
and  rendered  taut  by  a  turn  or  two  round  a  stout  nail.  The 
reflector,  no  matter  what  material  it  is  made  of,  must  be  suffi- 
ciently large  that,  when  the  eye  is  placed  at  the  position  of  the 
lens,  and  the  negative  removed,  nothing  but  the  reflector  can  be 
seen  through  the  aperture  in  the  shutter.  The  only  point  now 
needing  a  little  elucidation  is  that  of  the  easel  or  other  support 
for  the  sensitive  surface.  This  may  actually  be  an  easel,  as 
offered  by  some  commercial  firms.  We  use  an  arrangement  of  a 
large  printing  frame  measuring  24  by  20,  which  carries  a  sheet 
of  plate-glass  puttied  into  the  rebate.  Behind  this  is  placed  the 
ground-glass  focussing  screen,  the  centre  of  which  is  ruled  in 
small  squares  of  half  an  inch  with  lead  pencil,  and  then 
varnished  with  crystal  varnish  for  a  space  of  about  the  size 
of  a  quarter-plate  ;  this  is  used  with  a  compound  focusser  for 
obtaining  microscopically  sharp  enlargements.  The  ground  side 
of  the  glass  is  next  to  the  plate-glass,  and  consequently  facing 
the  lens,  just  as  in  an  ordinary  camera  ;  the  ground-glass  is  held 
at  the  sides  by  two  small  studs,  as  used  for  the  interior  of  dark 
slides.  The  printing  frame  fits  into  a  specially  made  stand, 
which  runs  on  a  couple  of  parallel  pieces  of  wood  on  the  table, 
and  is  instantly  clamped  at  about  the  right  distance  from  the 
lens  by  lever  cams,  fine  focussing  being  adjusted  by  means  of  a 
short  rack  and  pinion.  The  above  arrangement  is,  of  course, 
a  little  more  elaborate  than  actually  required,  as  a  printing  frame 
supported  in  any  way  so  as  to  be  absolutely  steady  when  placed 
upright,  and  also  parallel  with  the  negative,  is  sufficient.  What 
is  the  best  lens  for  enlarging  ?  is  a  question  we  often  see  asked. 
Well,  the  answer  is  very  easy — viz.,  that  lens  which  took  the 
negative.  But  this  answer  requires  a  little  modification.  If 
the  negative  to  be  enlarged  is  a  portrait,  then  a  portrait  lens  may 
be  used ;  but  the  back  lens  of  the  combination  must  be  placed 
next  to  the  negative.  The  most  useful  lens  is  undoubtedly 
the  doublet  of  the  rapid  rectilinear  type,  as  it  gives,  as  a  rule, 
excellent  marginal  definition.  A  single  or  landscape  lens  may 
also  be  used,  but  from  the  necessity  of  using  a  smaller  diaphragm 
it  is  obviously  slow  ;  in  this  case  the  convex  side  must  be  pre- 
sented to  the  negative,  the  plane  or  concave  surface  being 
towards  the  sensitive  surface.  The  diaphragm  should  be  about 
the  diameter  of  the  lens  in  front  of  the  concave  surface — that  is, 

163 


Enl] 


DICTIONARY  OF  PHOTOGRAPHY. 


between  the  lens  and  sensitive  paper.  There  is,  of  course,  some 
residuum  of  distortion  which  may  prove  troublesome  when 
enlarging  architectural  subjects.  In  the  case  of  the  rectilinear 
doublets,  it  is  immaterial  which  lens  of  the  combination  is  pre- 
sented to  the  negative. 

Apparatus  for  Enlarging  by  Artificial  Light. 
To  most  amateurs,  especially  those  engaged  in  business  during 
the  hours  of  daylight,  artificial  light  is  the  only  one  they  can 
employ  for  enlarging ;  hence  considerable  attention  will  be  paid 
to  this.  We,  first  of  all,  as  already  suggested,  divide  our  lights 
into  petroleum,  or  mineral  oil,  gas,  enriched  gas,  limelight,  mag- 
nesium, and  the  electric  light ;  and  we  shall  endeavour  to  describe 
the  arrangements  for  all,  but  must  premise  that  the  first  essentials 
for  successful  work  are  that  the  light,  no  matter  what  kind  it 
is,  must  be,  first,  small  in  dimensions,  and,  secondly,  actinic 
in  quality ;  the  first  gives  greater  sharpness,  the  latter  short 
exposures. 

Mineral  Oil  Lamps.  Opinions  differ  as  to  the  best  form  of 
lamp  for  enlarging,  most,  if  not  all,  commercial  apparatus  being 
provided  with  lamps  having  flat  wicks  turned  endwise  to  the 
condensers.  Here  again  we  find  a  divergence  of  opinion,  some 
preferring  two-wick,  some  three-wick,  others  four-wick  lamps  ; 
generally,  however,  three-wick  lamps  are  used.  We  have  used, 
with  good  results,  however,  a  round-wick  lamp,  or  so-called 
Argand  burner,  this  being  actually  a  Defries  lamp  of  forty-candle 
power.  The  burner  of  this  lamp  is  circular,  with  an  air  passage 
up  the  centre,  and  has  a  chimney  of  glass  contracted  just  above 
the  burner,  and  above  the  contraction  the  flame  appears  intensely 
luminous  and  solid  ;  it  is  at  this  point  that  the  flame  should  be 
used.  For  this  purpose  it  is  necessary  to  provide  the  lamp  with 
an  outer  case  of  brass  or  tin,  which  may  be  fitted  in  position  and 
slid  up  and  down,  without  in  any  way  touching  the  glass  chimney. 
The  tinned  sheet-iron  is  carried  up  above  the  glass  chimney  for 
some  distance  so  as  to  lengthen  the  chimney,  thus  creating  more 
draught,  therefore  more  perfect  combustion  of  the  oil  and  a 
more  actinic  light.  The  outer  sheet-iron  case  is  provided  with 
an  aperture,  circular,  of  half  an  inch  diameter ;  and,  on  looking 
into  this,  nothing  but  an  intensely  luminous  circle  of  white  flame 
is  seen.    No  matter  what  lamp  is  used,  the  circle  of  illumination 

164 


DICTIONARY  OF  PHOTOGRAPHY. 


[Enl 


thrown  by  the  objective  should  show  no  lines  of  variable  illumina- 
tion. The  most  important  thing  in  all  illumination  is  to  have  the 
radiant  a  point,  otherwise  we  are  troubled  with  parallax,  varying 
illumination,  and  want  of  sharpness  ;  but,  provided  the  degree  of 
amplification  be  not  too  great,  this  trouble  will  not  arise. 

Gas  and  Enriched  Gases.    Ordinary  gas,  unless  of  good  quality, 
is  not  so  suitable  as  gas  enriched  by  the  vapour  of  some  hydro- 
carbon.  The  commercial  form  of  albo-carbon  will  be  found  very 
suitable.  Mr. TraillTaylorhassuggestedaveryconvenient arrange- 
ment, "  which  consists  of  two  fish-tail  burners  separated  from  each 
other  by  the  extent  of  an  inch,  both  flames  having  their  flat  sides 
towards  the  condensers,  there  being  an  opaque  disc,  with  a 
circular  aperture  in  it  of  a  little  over  half  an  inch  in  diameter, 
placed  as  close  as  possible  up  against  the  foremost  flame  so  as 
to  reduce  its  effective  area.     The  position  of  this  aperture  must 
be  such  as  to  be  opposite  to  the  most  luminous  part  of  the  flame. 
The  second  flame  behind  the  anteVior  one  serves  to  confer  in- 
tensity, and  is  of  great  utility  ;  but  nothing  seems  to  be  gained 
by  a  third  burner.     The  gas  flame,  when  thus  enriched  by  the 
vapours  of  the  albo-carbon,  become  very  intense.    An  Argand 
flame  from  gas  thus  enriched  ought  to  yield  a  light  of  great 
excellence,  provided  it  has  a  smaller  flame  ascending  through 
its  centre,  and  that  provision  is  made  to  condense  it  by  diminish- 
ing its  diameter,  either  by  a  brass  solar  cap  to  cause  a  strong 
current  of  air  to  impinge  upon  the  flame  a  little  above  the 
burner,  or  by  a  contraction  in  the  glass  chimney.  Whiteness 
and  intensity  in  such  a  case  are  increased  by  a  judicious  lengthen- 
ing of  the  chimney  to  increase  the  draught.    The  area  of  the 
flame  must,  however,  be  reduced  by  the  expedient  already  pointed 
out."    The  Welsbach  or  Incandescent  gas  burner  is  one  par- 
ticularly adapted  for  enlarging,  as  the  light  emitted  is  exception- 
ally rich  in  actinic  rays,  and  the  exposure  thereby  considerably 
shortened.     In  some  experiments  in  connection  with  this  light 
we  found  that  with  the  ordinary  household  gas  supply  the 
exposure  was  cut  down  to  one-quarter  of  that  with  an  ordinary 
three-wick  lamp. 

Limelight.  This  is,  of  course,  one  of  the  most  convenient  of 
all  sources  of  light,  and  is  so  well  known  as  to  need  but  little 
description. 

Magnesium.    So  far  as  we  know  there  is  no  commercial 
165 


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DICTIONARY  OF  PHOTOGRAPHY. 


apparatus  for  utilising  magnesium  as  an  illuminant  with  con- 
densers, though  of  course  it  would  be  quite  possible  to  utilise 
any  ordinary  enlarging  lantern  with  a  clockwork  arrangement  for 
feeding  the  magnesium  to  a  small  spirit  flame,  so  as  to  keep  the 
radiant  point  at  one  particular  distance  from  the  condensers. 

The  Electric  Light.  Few  amateurs,  or  even  professionals,  can 
afford  the  necessary  outlay  for  this  light,  the  cost  of  even  a 
primary  battery  or  accumulators  being  considerable.  In  many 
parts  of  London,  however,  the  wires  for  electric  lighting  are  now 
laid  along  the  principal  thoroughfares,  and  it  would  therefore 
be  easy  to  connect,  and  the  cost  of  installation  is  about  thirty 
shillings  per  lamp.  A  portable  battery,  the  Schanchieff,  has 
been  used  for  lantern  work,  and  would  also  answer  well  for 
enlarging.  The  apparatus  for  enlarging  by  artificial  light  bears 
some  resemblance  to  the  ordinary  or  so-called  magic-lantern. 
It  is  immaterial  of  what  nature  or  substance  the  body  of  the 
lantern  is,  provided  it  be  light-tight  and  strong.  Russian  or 
sheet-iron,  copper,  or  wood  with  metal  lining — all  are  used  by 
commercial  firms.  The  enlarging  apparatus  practically  consists 
of  a  camera  attached  to  an  optical  lantern,  focussing  being 
effected  by  rack  and  pinion.  We  need  make  no  further  mention 
of  these,  except  that  we  shall  later  give  a  sketch  showing  how 
an  ordinary  magic-lantern  may  be  adapted  for  enlarging. 

The  Condensers.  The  function  of  the  condenser  is  to  collect 
the  rays  of  light  and  refract  them  through  the  negative.  The 
usual  form  of  condenser  employed  is  two  plano-convex  lenses 
placed  side  by  side,  with  the  convex  surfaces  nearly  touching. 
The  first  question  to  decide  in  purchasing  an  enlarging  lantern 
is,  What  size  condensers  are  required  ?  as  the  size  of  the  con- 
densers governs  the  price.  It  is  a  question  which  has  often 
been  asked  by  beginners  as  to  what  size  condenser  will  cover 
a  certain-sized  plate.  This  is  by  no  means  difficult  to  decide. 
All  that  it  is  requisite  to  do  is  to  measure  the  diagonal  of  the 
negative  in  question,  and  this  diagonal  will  be  the  diameter  of 
the  required  condenser.  In  practice  it  is  always  advisable  to 
allow  an  extra  quarter  or  half  an  inch  where  this  does  not  add 
too  much  to  the  cost.  Mr.  Hughes  has  introduced  a  rectangular 
condenser.  In  selecting  condensers,  the  most  important  points 
to  note  are,  first,  to  see  that  they  are  as  free  as  possible  from 
colour ;  secondly,  that  the  one  next  the  negative  is  free  from 

166 


DICTIONARY  OF  PHOTOGRAPHY. 


[Enl 


air-bubbles  and  striae ;  thirdly,  that  they  are  not  set  too  tightly 
in  their  mountings,  or  when  heated  from  the  light  they  will  crack. 

Enlarging  by  Artificial  Light  without  Condensers.  This  is 
a  procedure  which  will  commend  itself  to  many  an  operator, 
because  the  necessary  apparatus  may,  in  many  cases,  be  knocked 
up  from  odds  and  ends  in  odds  and  ends  of  spare  time.  Thus 
we  utilised  an  old  square  sugar  case  which  cost  4^.,  and  the 
sheet-tin  to  line  it  gd.,  the  lamp  15^.,  odds  and  ends,  such  as 
screws,  ground-flashed  opal  glass,  another  2s. ;  so  that  for  i8.y. 
an  enlarging  apparatus  was  obtained,  which  worked  well  for  over 
two  years.  As  condensers  are  usually  rather  costly,  the  follow- 
ing ingenious  arrangement,  which  dispenses  with  them  altogether 
may  be  utilised  ;  it  is  suggested  by  Major  Barrington  Baker,  in 


Fig.  36- 


the  British  Journal  of  Photography  tor  1888.  Fig.  37  on  next 
page  is  a  rough  reproduction  of  Major  Baker's  diagram,  and  the 
following  precis  is  given  of  his  directions.  The  case  is  made 
of  £-in.  deal,  with  a  hole,  n,  6\  by  4%  for  negative,  or  made  the 
size  desired.  l,  a  Beige  lamp  of  42-candle  power,  is  placed  in 
the  case  through  the  door  d,  half  a  dozen  holes  (a  a)  being  bored 
in  the  bottom  of  the  box  for  ventilation.  An  opal  globe  is  used 
to  diffuse  the  light  ;  the  negative  is  placed  film  side  outwards  in 
a  rebate  at  n,  and  held  in  its  place  by  two  small  turn-buckles  ;  the 
camera  may  be  used,  or  a  specially  made  pair  of  bellows.  The 
exposure  is,  of  course,  prolonged  with  rapid  papers,  being  from 
10  to  15  mins.  The  author  would  suggest  as  an  improvement 
upon  this  that  the  case  be  lined  throughout  with  tin,  and  a  sheet 
of  ground  glass  or  opal  be  placed  before  the  negative,  and  that 
a  parabolic  reflector  be  used.    Some  of  the  modern  cameras  will 

167 


Enl] 


DICTIONARY  OF  PHOTOGRAPHY. 


be  found  utterly  useless  for  enlarging,  the  pull  of  the  bellows,  or 
the  greatest  distance  they  will  stretch,  being  very  short ;  then 
the  following  arrangement,  now  always  used  by  the  author,  will 
take  their  place  : — Obtain  some  black  twill,  I  yard  in  width  and 
length,  and  cut  it  into  four  pieces  in  the  following  manner  (it  is 
better  to  cut  paper  pattern  first,  in  case  of  error) : — Fold  the 
cloth  in  half,  and  again  in  half,  so  as  to  give  four  pieces  9  ins. 
wide  and  36  ins.  long ;  now  cut  two  slanting  strips  from  each, 
commencing  at  2  ins.  wide,  and  narrowing  down  to  the  other  end  ; 
this  will  give  four  pieces  of  cloth  36  ins.  long — 9  ins.  wide  at  one 


f 


L 


C 

j  3 

Fig.  37- 


end,  and  narrowing  to  5  ins.  at  the  other.  Have  these  sewn 
together  by  the  edges,  so  as  to  form  a  conical  sleeve,  which  will 
take  the  place  of  bellows  36  ins.  long.  At  the  wide  end  nail  a 
frame  of  wood  large  enough  to  take  the  negative,  and  at  the 
narrow  end  a  piece  of  wood  to  take  the  lens,  or  the  camera 
front  may  be  utilised  for  this  purpose.  It  will  not  be  necessary 
to  pleat  it  like  bellows,  but  it  can  be  finely  pleated  at  intervals, 
and  safety  pins  used  to  hold  the  pleats  together  when  required 
to  shorten  the  distance,  so  the  pleats  can  easily  be  let  out  when 
required,  or  pieces  of  elastic  can  be  run  along  the  edges  to  serve 
the  same  purpose.     The  possessor  of  a  magic-lantern  can  easily 

168 


DICTIONARY  OF  PHOTOGRAPHY.  [Elll 

utilise  that,  no  matter  what  size  the  condenser,  if  a  sleeve  of 
black  cloth  is  made  to  fasten  at  one  end  round  the  lantern 
objective  and  at  the  other  to  the  camera,  the  negative  being 
placed  in  the  position  of  the  focussing  glass  of  the  camera. 
Where  the  operator  can  utilise  gas  or  several  oil-lamps  it  is  only 
necessary  to  place  between  them  and  the  negative  a  sheet  of 
flashed  opal  glass  ground  on  the  flashed  side,  or  a  piece  of 
ground  glass  coated  on  the  ground  side  with  an  emulsion  of 
sulphate  of  baryta  in  gelatine  or  of  finely  sifted  carbonate  of  lead. 
When  using  an  ordinary  lantern  it  is  absolutely  necessary  that 
no  stray  light  should  find  its  way  out  of  the  same ;  therefore  it 
is  nearly  always  necessary  to  enclose  it  in  an  outer  box.  This 
is  a  point  which  requires  careful  attention,  or  foggy,  degraded 
whites  will  ensue  in  the  resulting  enlargement. 

Focussing. 

It  may  be  taken  as  an  accepted  axiom  that  the  nearer  the 
light  is  to  the  condensers  and  the  nearer  the  condensers  to  the 
negative  the  greater  will  be  the  illumination,  and  the  greater 
the  distance  between  the  lens  and  sensitive  surface  the  less  the 
illumination  ;  or,  in  other  words,  the  larger  one  enlarges,  the 
longer  one  must  expose,  everything  else  being  constant.  There 
is  one  precaution  necessary  when  using  condensers,  or  even 
artificial  light  of  any  kind  with  condensers,  and  that  is,  to  see 
that  everything  is  gradually  warmed.  Don't  turn  your  light  on 
full  power  at  once,  and  place  it  close  up  to  the  condenser,  and 
then  be  surprised  if  your  condenser  cracks.  Warm  everything 
gradually  by  having  your  light  low  and  some  distance  from  the 
condenser,  and  gradually  reduce  the  distance  and  increase  the 
light.  It  will  be  obvious  to  the  merest  tyro  in  enlarging  that 
the  farther  the  lens  is  from  the  sensitive  paper  the  larger  the 
image,  and  vice  versa ;  and  also  that  there  are  certain  distances 
which  bear  a  certain  relation  one  to  the  other,  so  that  when 
enlarging,  the  distance  between  the  negative  and  lens  and  lens 
and  sensitive  surface  bear  a  strict  relation  to  one  another.  The 
approximate  distance  between  the  negative  and  lens  and  lens 
and  paper  may  be  found  from  the  following  formula  : — 

(1)  d=f+S. 

(2)  D=(»+  l)f. 

169 


Enl]  DICTIONARY  OF  PHOTOGRAPHY. 

Wherein  d  =  the  distance  between  the  negative  and  lens. 

D  =  the  distance  between  the  lens  and  sensitive  surface. 

/  =  the  equivalent  focus  of  the  lens. 

n  =  the  number  of  times  of  enlargement. 
Or  to  the  non-mathematic  mind  we  will  put  it  in  another  way. 
To  find  the  distance  between  the  lens  and  sensitive  surface, 
add  one  to  the  number  of  times  (linear  measurement)  the 
negative  is  to  be  enlarged,  and  multiply  by  the  focus  of  the 
lens.  To  find  the  distance  between  the  lens  and  negative, 
divide  the  product  of  the  above  calculation,  or  the  distance 
between  the  lens  and  sensitive  surface,  by  the  number  of  times 
of  enlargement,  and  the  quotient  will  be  the  distance  between 
negative  and  lens.  For  example,  it  is  required  to  enlarge  a 
quarter-plate  negative  to  16x12  with  a  6-inch  lens.  4^x3! 
enlarged  to  16  x  12  —4.  times  (linear).  The  distance  will  be  then 
approximately  (4+  1)  x  6  =  30  inches,  between  lens  and  sensitive 
surface.  To  find  the  distance  between  lens  and  negative 
30-r4  =  7-£.  To  save  trouble,  however,  there  are  well-known 
tables  which  have  been  calculated  for  enlargements  with  lenses 
of  varying  foci,  and  one  will  be  found  in  the  Appendix.  The 
distances  given  in  the  tables  will  be  found  to  be  approximately 
correct  ;  but  in  all  cases  accurate  focussing  should  be  obtained 
by  adjustment  of  the  screen  or  lens  by  rack  and  pinion.  Whilst 
many  operators  are  content  to  use  merely  a  white  piece  of 
paper,  and  to  focus  from  the  front,  it  will  be  found  far  pre- 
ferable to  use  the  ground-glass  screen  and  compound  focusser 
above  described.  In  all  cases  where  marginal-  definition  is 
defective,  stops  or  diaphragms  must  be  used,  exactly  as  in  field 
work.  Having  obtained  a  sharp  focus,  the  next  operation  is 
placing  the  sensitive  paper  in  position.  The  methods  adopted 
for  this  are  slightly  different,  some  operators  preferring  to  use 
a  cap  in  which  a  piece  of  yellow  or  ruby  fabric  or  glass  is 
placed,  so  as  to  illuminate  the  surface  focussed  on.  Others, 
again,  cap  the  lens  as  usual,  and  use  a  ruby  lantern  to  place 
the  paper  in  position  ;  we  prefer  the  former  plan,  because,  when 
orange  glass  is  used  in  the  cap,  it  enables  one  to  ascertain 
whether  any  alteration  in  focal  sharpness  of  the  image  takes 
place,  as  this  may  sometimes  occur  from  the  sensitive  paper 
buckling.  Another  point  is  the  method  of  fastening  the  sensitive 
surface  to  the  easel  board  if  this  be  used.    Of  course,  if  the 


dictionary  of  photography.  [Enl 

large  printing  frame  be  used,  as  we  have  suggested,  there  will 
be  no  difficulty  about  this  point  ;  but  when  the  paper  has  to  be 
affixed  to  a  board  there  is  a  slight  difficulty.  One  plan  we  have 
tried  with  success  has  been  to  have  a  quarter-inch  groove  cut 
in  the  face  of  the  easel  board  along  one  side  or  the  top,  and  in 
the  groove  a  piece  of  stout  steel  or  copper  wire,  preferably  the 
former,  is  placed,  and  the  ends  of  the  wire  are  turned  over  the 
sides  of  the  board,  and  passed  through  stout  brass  eyelets,  and 
then  provided  with  a  screw  thread,  on  which  fits  a  milled  nut. 
The  action  of  this  wire  is  merely  to  clip  the  paper  in  the  groove, 
and  if  such  a  groove  is  placed  at  top  and  bottom  of  easel  board, 
it  is  possible  to  clip  the  paper  firmly  under  one  groove,  and  then 
to  pass  it  under  the  other,  and  stretch  it  taut,  and  then  screw  up 
the  milled  nuts.  Another  method  is  to  use  large-headed  drawing 
pins  at  the  four  corners,  or  to  use  broad  indiarubber  bands. 
The  advantage  of  using  some  broad  surface  like  the  head  of  a 
drawing  pin  is  that  it  enables  one  to  accurately  determine 
whether  the  whites  of  the  enlargement  are  pure  or  fogged. 
Surgeon-General  J.  L.  Ranking  suggested  in  the  Amateur 
Photographer  of  November  28th,  1890,  curving  the  paper,  and 
gives  the  following  directions  : — "  I  have  applied  this  principle 
to  my  easel  in  the  following  manner  :  The  ce?itre  of  a  sheet  of 
paper,  16x12  in.,  my  usual  size  for  enlarging  from  a  quarter-plate 
negative,  being  pinned  to  the  easel  top  and  bottom,  a  wedge- 
shaped  piece  of  wood  was  passed  beneath  one  end  of  the  paper 
till  the  margin  of  the  picture  was  equally  sharp  with  the  centre. 
The  distance  to  which  the  margin  was  advanced  towards  the 
lens  was  found  to  be  1  in.  Two  pieces  of  wood  were  then 
prepared,  12  ins.  long  and  6  ins.  wide.  They  were  then  planed 
down  so  as  to  form  two  wedge-shaped  pieces  1  in.  deep  at  outer 
and  ^  in.  at  inner  edge.  These  were  then  screwed  down  upon 
the  easel,  and  to  them  a  thin  piece  of  cardboard  fixed,  thus 
forming  the  required  curved  surface.  Upon  the  picture  being 
sharply  focussed  the  sheet  of  sensitised  paper  is  pinned.  With 
Ilford  rapid  paper  and  the  artificial  light  I  use,  which  I  shall 
presently  describe,  and  using  an  R.R.  lens,  8-in.  focus,  at  full 
aperture,  an  exposure  of  from  8  to  10  seconds  suffices  to  enlarge 
from  a  quarter-plate  up  to  16x12.  If  a  longer  exposure  be 
necessary,  as  it  is  in  enlarging  from  landscape  negatives,  into 
which  skies  have  to  be  introduced,  the  lens  can  be  stopped 

i7l 


Enl]  DICTIONARY  OF  PHOTOGRAPHY. 

down  to  any  extent,  the  exposure  being  calculated  upon  the 
well-known  ratios  of  the  squares  of  the  diameters  of  the  stops, 
or  a  slow  paper  can  be  used.  The  artificial  light  I  use  is  the 
Welsbach  incandescent  gaslight,  said  to  be  16-candle  power,  and 
I  find  it  most  convenient.  It  is  attached  to  the  nearest  gas- 
bracket by  a  flexible  tube,  and  it  can  be  lighted  and  extinguished 
in  a  moment." 

Exposure. 

Having  obtained  a  critically  sharp  image,  the  next  point  to 
decide  is  what  exposure  is  required ;  and  the  determination  is 
perhaps  quite  as  difficult  and  equally  as  important  as  in  negative 
making.  Various  methods  have  been  suggested,  but  before 
entering  upon  these  it  would  be  advisable  to  consider  the  factors 
which  govern  the  duration  of  exposure  : — (i)  The  actinic  power 
of  the  light ;  (2)  The  density  of  the  negative ;  (3)  The  intensity 
ratio  of  the  stop  ;  (4)  The  number  of  times  of  enlargement, 
or  the  distance  between  the  lens  and  sensitive  surface  ;  (5)  The 
sensitiveness  of  the  material  on  which  the  enlargement  is  made. 

(1)  The  Actinic  Power  of  the  Light.  The  only  satisfactory 
method  of  determining  this  is  by  the  aid  of  an  actinometer ;  and 
the  most  satisfactory,  and,  in  fact,  the  only  ones  to  use  are  those 
based  upon  the  action  of  light  upon  bromide  of  silver  paper 
impregnated  with  solution  of  nitrite  of  potassium.  There  are 
two  such  actinometers  in  the  market,  Stanley's  and  Watkins', 
in  which  the  actinic  power  of  the  light  is  gauged  by  the  time  a 
bromide  of  silver  paper  prepared  as  above  takes  to  match  a 
standard  tint.  In  connection  with  this  we  would  point  out 
that  it  is  said  to  be  extremely  difficult  to  match  the  standard 
tint ;  but  the  following  quotation  from  the  instructions  issued  by 
the  maker  of  the  latter  actinometer  is  worth  consideration  : — 
"  In  testing  the  light  no  notice  should  be  taken  of  the  exact 
colour  of  the  sensitive  paper,  which  may  vary  slightly  with  the 
humidity  of  the  air ;  the  depth  of  tint  is  the  important  point. 
The  paper  darkens  rapidly  in  light ;  up  to  a  certain  point  it  is 
lighter  than  the  standard  tint,  after  this  point  it  is  darker.  The 
point  when  it  is  neither  lighter  nor  darker  is  that  to  be  timed." 
To  prepare  a  somewhat  similar  actinometer  it  is  only  necessary  to 
soak  ordinary  bromide  paper  in  a  10  per  cent,  solution  of  nitrite 
of  potassium,  and  then  to  dry  it  in  the  dark.    A  small  piece  is 

172 


DICTIONARY  OF  PHOTOGRAPHY. 


[Enl 


allowed  to  darken  in  daylight,  and  the  time  that  it  takes  to 
deepen  to  a  tint  which  may  be  arbitrarily  chosen  accurately 
counted,  or  timed  by  a  watch.  This  tint  should  then  be  matched  in 
water-colours,  and  painted  on  a  strip  of  paper.  It  must  be  noted, 
however,  that  the  tint  of  the  paint  when  dry  must  agree  with 
the  tint  of  the  darkened  paper.  Now,  to  use  this  actinometer, 
paste  the  strip  of  painted  paper  on  the  top  of  a  cardboard  match- 
box, place  inside  the  box  the  sensitive  paper  soaked  in  the 
nitrite  solution,  and  draw  a  small  piece  out  and  allow  it  to 
darken  at  a  distance  of  about  18  ins.  from  a  No.  5  Bray's  gas 
burner  turned  full  on  without  flaring  behind  the  half-tones 
of  a  negative,  noting  accurately  the  number  of  seconds  it  takes 
to  darken  to  the  standard  tint.  Now  take  a  sample  of  some 
bromide  paper,  Eastman's,  for  instance,  and  expose  half-a-dozen 
sheets  of  the  same  paper  behind  the  negative  at  the  same 
distance,  18  ins.,  giving  various  exposures,  then  on  developing 
these  six  sheets  it  will  be  possible  to  pick  out  one  print  correctly 
exposed ;  and  from  this  we  can  establish  one  factor,  which  will 
enable  us  to  calculate  other  exposures  under  other  conditions. 
Thus  if  the  actinometer  paper  takes  10  seconds  to  darken  to  the 
standard  tint,  and  we  find  8  seconds  the  correct  exposure  for 
the  said  negative  at  18  ins.  from  the  gas  burner,  it  will  not  be 
difficult  to  calculate  the  exposure  for  any  distance  or  any  more 
or  less  actinic  light.  For  example,  the  exposure  required  for 
the  same  negative  at  a  distance  of  36  ins.  from  the  same  gas 
burner  is  easily  calculated  by  the  rule  that  the  exposure  alters 
as  the  square  of  the  distance  between  the  light  and  sensitive 
paper.  The  exposure  required  at  18  ins.  =  8  sees.,  .*.  the  ex- 
posure required  at  36  ins.  will  be  in  the  ratio  of  18'-':  36-,  or  as 
324 :  1296.  Now  324  :  1296  are  as  1  :  4,  .*.  if  the  exposure  in  the 
first  case  =  8  sees.,  the  exposure  in  the  second  case  =  8x4  =32 
sees.  This  will  explain  the  use  of  the  actinometer,  and  deter- 
mine the  first  factor. 

(2)  The  Density  of  the  Negative.  It  is  difficult  to  accu- 
rately determine  this,  as  the  actual  deposit  of  silver  does 
not  alone  represent  the  density  of  the  negative.  The  colour 
of  the  deposit,  and  the  presence  or  absence  of  stain  in  the 
film,  will  also  influence  this  factor  ;  but  by  using  the  actino- 
meter as  suggested  under  the  first  factor  we  practically 
determine  the  second  factor  also. 

*73 


Enl] 


DICTIONARY  OF  PHOTOGRAPHY. 


(3)  The  Intensity  Ratio  of  the  Stop.  Most  workers  know 
the  usual  definition  of  this  term,  which  is  the  ratio  the 
aperture  of  the  stop  or  diaphragm  bears  to  the  equivalent 
focus  of  the  lens ;  when  using  a  lens  for  enlarging,  however, 
we  never  use  it  at  its  equivalent  focus,  the  focus  altering 
with  the  degree  of  enlargement.  Therefore  we  have  to  calcu- 
late anew  the  intensity  ratio  of  our  stops  for  the  new  focus. 
Thus,  supposing  we  are  using  an  8^-in.  focus  lens  for  an 
enlargement  of  a  quarter-plate  to  12  by  12,  or,  in  other  words, 
if  we  are  enlarging  four  times,  the  focus  of  our  8J-in.  lens 
becomes  io|  in.  ;  therefore  all  the  diaphragms  will  be  pro- 
portionately reduced  in  ratio  diameter.  It  will  always  be  found 
more  convenient  if  diaphragms  of  definite  diameters  are  used. 
Thus  special  diaphragms  of  i-in.  diameter  aperture  or  £-in. 
diameter  aperture  can  be  obtained ;  and  it  is  thus  easy  to  cal- 
culate at  once  the  new  intensity  ratio,  without  troubling  to 
measure  the  diameter  every  time. 

(4)  The  Number  of  Times  of  Enlargement,  or  the  Distaiice 
between  the  Lens  and  Sensitive  Surface.  It  is  requisite  to  take 
into  account  this  factor,  because,  according  to  the  well-known 


Fig.  38. 


rule,  the  intensity  of  illumination  011  a  given  surface  is  inversely 
as  the  square  of  its  distance  from  the  source  of  light,  or,  in  other 
words,  the  greater  the  distance  of  the  sensitive  surface  from  the 
lens  the  longer  the  exposure.  This  is  very  clearly  seen  from  the 
above  diagram.  Let  l  be  the  source  of  light,  and  if  we  place 
the  bromide  paper  at  1.,  12  ins.  from  the  light,  and  we  find  the 
exposure  to  be  45  seconds,  when  we  place  the  paper  at  n„  nr., 

174 


DICTIONARY  OF  PHOTOGRAPHY. 


iv.,  respectively— at  24,  36,  and  48  ins.,  the  exposure  will 
not  be  45,  90,  135,  and  180  seconds,  but  in  the  proportion  of 
i,  22,  32,  42,  or  45,  180,  395,  and  720  seconds  respectively. 

(5)  The  Sensitiveness  of  the  Material  on  which  the  Enlarge- 
ment is  made.  This  has  been,  to  a  great  extent,  a  matter  of  con- 
jecture hitherto  ;  but  I  give  a  table  of  relative  speeds  compiled  by 
Mr.  Alf.  Watkins  for  use  with  his  exposure  meter,  merely  noting 
that  the  exposures  will  be  in  inverse  ratio  to  the  P.  numbers. 

P.  Numbers.  Exposure. 


Eastman  slow 

6 

6§ 

,,  rapid 

...  40 

1 

Morgan  and  Kidd  ... 

...  15 

Anthony  rapid 

...  50 

Ilford  slow  ...   

3 

13^ 

,,    rapid  ... 

...  30 

li 

Dr.  Just   

4 

10 

Mawson  ...   

6 

65 

The  first  column  shows  the  P.  number  obtained,  and  the  second 
one  the  relative  exposures  required.  Before  closing  this  note  it 
would  be  but  fair  to  give  to  Mr.  Ferrero  the  honour  of  having 
first  drawn  out  a  table  of  exposures  for  enlarging,  which  is  given 
in  the  Appendix.  Full  directions  for  developing,  clearing,  fixing, 
etc.,  will  be  found  included  under  Bromide  Paper  (</.v.). 

Vignetting,  Printi7ig-in    Clouds,  Reducing,  and  Intensifying 
Prints. 

To  vignette  enlargements  is  not  a  difficult  matter,  and  for 
portraits  the  result  is  sometimes  more  pleasing  than  without  the 
same.  For  vignetting  it  is  only  requisite  to  take  a  piece  of  card- 
board the  same  size  as  the  enlargement  is  to  be,  and  cut  in  the 
cardboard  an  opening  the  shape  of  the  desired  vignette,  but 
small ;  it  should  not  be  much  larger  than  the  lens  aperture. 
The  size  of  the  vignette  is  determined  by  the  distance  of  the 
vignetting  paper  from  the  sensitive  surface,  as  the  nearer  this  the 
smaller  the  vignette,  and,  vice  versa,  the  nearer  the  lens  the 
larger  the  vignette.  The  edges  of  the  vignetting  opening  in  the 
card  need  not  be  serrated,  as  the  vignette  is  softened  by  keeping 
the  card  constantly  moving  between  the  lens  and  sensitive 
surface.    Many  operators,  however,  prefer  to  use  a  vignetting 

175 


Elll]  DICTIONARY  OF  PHOTOGRAPHY. 

shape  with  deeply  serrated  edges  ;  and  this  is  so  adjusted  as  to 
give  a  pleasing  soft  outline  on  the  focussing  easel  or  screen  ; 
and  this  method  is  preferred  because  the  moving  vignette  is 
stated  to  be  the  cause  of  blurring  of  the  outlines  from  double 
vibration,  a  charge  we  have  not  found  substantiated.  Enlarge- 
ments of  landscapes  are  always  improved  by  the  addition  of 
clouds  ;  and  if  these  are  non-existent  in  the  negative,  a  separate 
suitable  negative  should  be  used.  There  are  several  methods 
of  inserting  clouds,  which  are  given  below.  One  method  is  to 
make  a  small  transparency  by  contact  printing  from  the  negative 
to  be  enlarged,  and  make  a  transparency  of  the  cloud  negative, 
masking  out  the  landscape.  The  two  will  then  be  bound  film  to 
film,  care  being  taken  that  the  clouds  are  not  reversed  in  lighting, 
and  then  making  an  enlarged  negative  from  this.  Another  method 
is  to  make  a  silver  print  from  the  small  negative,  and  carefully 
cut  out  the  landscape,  and  allow  the  two  pieces  of  the  silver  print 
to  blacken  completely  in  the  sun.  Then  fasten  the  landscape 
print  on  to  the  cloud  negative,  and  the  sky  print  on  to  the 
original  negative,  or  else  paint  out  the  sky  with  some  opaque 
colour.  Having  focussed  and  exposed  the  landscape  negative, 
cap  your  lens  with  a  piece  of  orange  glass,  and  carefully  adjust 
your  cloud  negative  till  it  is  in  exactly  the  same  position  as  the 
first  negative,  and  the  outline  agrees  with  that  of  the  view,  which 
may  be  marked  at  the  edges  of  the  sensitive  paper ;  then  expose. 
Another  method  is  to  expose  as  usual  for  the  landscape,  develop, 
and  clear ;  then,  without  fixing,  place  again  on  the  easel,  and 
with  the  yellow  cap  on  the  lens,  focus  the  clouds  from  the  cloud 
negative  and  adjust  till  in  correct  position,  and  then  cover  up  the 
landscape  with  a  mask  cut  from  ruby  paper,  and  expose  for  the 
clouds.  The  exposure  for  clouds  should  be  very  short,  so  as  not 
to  make  them  too  dark  and  prominent ;  practically  about  one- 
fourth  of  the  exposure  required  for  the  view  will  be  correct  for 
the  clouds.  Trees,  church  steeples,  and  other  objects  projecting 
into  the  sky  may  be  practically  disregarded,  as  these  will  print 
over  the  sky  and  give  a  more  realistic  effect.  To  prevent  too 
sharp  a  line  of  demarcation,  the  mask,  or  a  sheet  of  cardboard 
cut  roughly  to  shape,  may  be  gently  moved  up  and  down  near 
the  sensitive  surface  to  shade  the  landscape  into  the  sky.  In 
enlarging,  as  in  every  other  photographic  process  where  success 
depends  upon  a  variable  quantity  as  personal  skill,  care,  and 

176 


DICTIONARY  OF  PHOTOGRAPHY. 


[Enl 


judgment,  failures  are  unfortunately  too  often  met  with.  We 
shall  therefore  proceed  to  consider  these  in  the  order  of  the 
several  operations. 

The  enlargement  is  out  offoctcs,  especially  at  the  edges.  This 
fault  is  due  to  non-coincidence  of  the  plane  of  the  sensitive 
surface  with  that  of  the  focussing  paper  or  ground  glass.  This 
may  be  remedied  by  focussing  as  usual,  then  placing  a  piece  of 
orange  glass  over  the  lens,  fixing  the  sensitive  surface  in  position, 
and  examining  the  focus  ;  and,  if  it  appear  sharp,  exposing  and 
examining  the  developed  print.  It  may  also  be  caused  by  the 
sensitive  paper  buckling  or  not  lying  quite  flat,  and  also  by 
using  too  large  an  aperture  of  the  lens.  The  former  may  be 
prevented  by  straining  the  paper  very  tightly,  and  the  latter 
obviously  by  the  insertion  of  a  diaphragm.  It  may  also  be 
caused  by  using  too  large  a  flame  surface  as  illuminant.  Other 
failures  are  treated  of  under  Bromide  Paper  (q.v.). 

Sensitising  Canvas  for  E?ilarge?nents. 
A  writer  in  the  Photo graphische  Correspondenz  gives  the  fol- 
lowing methods  of  sensitising  canvas  for  enlarging  direct.  The 
canvas  must  first  be  well  washed  with  a  solution  composed  of 

Liquid  ammonia -88o        ...       ...       ...      10  parts. 

Alcohol  (methylated)    40 

A  clean  pad  of  linen  should  be  used  till  the  film  shows  no  sign  of 
greasiness,  and  is  then  allowed  to  dry  thoroughly.  The  follow  - 
solution  is  then  made  : — 

Gelatine    ...       ...       7  parts. 

This  is  allowed  to  soak  in 

Distilled  water       ...       ...       ...       ...    250  parts 

till  soft,  and  then  dissolved  by  the  aid  of  a  gentle  heat.  In  the 
meantime  take 

Fresh  egg  albumen   50  parts 

and  mix  with 

Distilled  water       ...    125  parts. 

Add 

Potassium  iodide    ...       ..,       9  parts. 

Ammonium  bromide         ...       ...       ...  4 

Ammonium  chloride         ...       ...       ...  1*25 

177  N 


Enl] 


DICTIONARY  OF  PHOTOGRAPHY. 


Beat  the  solution  well,  allow  to  stand  for  about  one  hour,  filter 
through  flannel,  and  add  to  it 

Distilled  water    125  parts 

and  the  solution  of  gelatine  prepared  as  above.  The  solution  is 
flowed  over  the  surface  of  the  canvas,  or,  preferably,  applied  with 
a  Buckle  or  Blanchard  brush,  or  small  piece  of  sponge.  The 
coated  canvas  is  then  allowed  to  dry,  and  several  thus  prepared 
may  be  stored  for  use,  and  sensitised  as  required  by  the  fol- 
lowing solution  : — 

Silver  nitrate    20  parts. 

Glacial  acetic  acid   10  ,, 

Distilled  water   240  ,, 

A  small  quantity  of  this  is  poured  on  to  the  gelatinised  canvas, 
and  evenly  distributed  with  a  Buckle  brush,  and  exposed  while 
still  wet,  allowing  about  seventy-five  seconds  to  elapse  between 
sensitising  and  exposing.  This  is  fairly  sensitive,  about  sixty 
seconds  being  required  for  a  good  light  from  a  clear  sky  with  an 
ordinary  negative.  When  the  exposure  is  complete,  develop 
with 

Gallic  acid  ,     3-5  parts. 

Lead  acetate  ...       ...       ...       ...       -6  „ 

Distilled  water       ...    ...    250  ,, 

Apply  to  the  canvas  in  the  same  manner  and  with  the  same 
brush  as  used  for  the  sensitising  solution.  When  sufficiently 
dense,  rinse,  and  fix  face  downwards  in 

Hyposulphite  of  soda       ...       ...       ...     20  parts. 

Water    100  „ 

Enlargements  on  Opal  and  Glass. — Enlarged  Negatives. 

Enlarging  on  to  opal  glass  or  dry  plates  presents  no  difficulties 
after  enlarging  upon  paper  has  been  mastered,  greater  care  only 
being  necessary  to  avoid  mistakes  and  failures,  as  the  cost  of 
opals  or  dry  plates  is  considerably  more  than  with  bromide  paper. 
Most  manufacturers  include  with  each  box  of  opals  trial  sheets 
of  bromide  paper,  which  may  be  used  for  test  exposures,  as 
described  previously.    For  enlarging  on  dry  plates  the  slowest 

176 


DICTIONARY  OF  PHOTOGRAPHY.  [Enl 

brand  possible  should  be  obtained,  the  so-called  lantern  plate 
being  the  most  suitable.  All  other  operations  of  developing, 
clearing,  and  fixing,  are  precisely  the  same,  with  one  slight 
exception.  Enlargements  on  paper  are  usually  seen  by  reflected 
light,  whereas  enlargements  on  opal  may  be  examined  by  reflected 
or  transmitted  light,  and  enlargements  on  dry  plates  are  always 
viewed  by  transmitted  light.  For  this  reason  enlargements  on 
opal  and  larger  transparencies  on  dry  plates  must  be  developed 
till  they  look  dense  enough  by  transmitted  light,  and  they  will 
probably  looked  "bunged-up  "  in  the  shadows  by  reflected  light ; 
therefore  their  density  must  be  judged  by  holding  them  up  to 
the  dark-room  window  or  lamp,  just  as  with  negatives.  When 
making  large  transparencies  on  dry  plates  by  enlarging,  we  are 
enabled  to  use  both  pyrogallol  and  quinol,  and  obtain  a  warmer 
tone  than  when  they  have  to  be  examined  by  reflected  light. 
Two  formulae  are  given  in  the  Appendix  for  this  special  purpose, 
the  resulting  image  being  a  fine  purple  by  transmitted,  but  a 
hideous  brown  by  reflected  light.  Other  methods  of  obtaining 
warmer  tones  will  be  given  later  on.  When  many  enlarged  prints 
from  one  negative  are  required,  it  will  often  be  found  advanta- 
geous to  make  an  enlarged  negative  and  print  by  contact  from 
this.  For  this  purpose  it  is  obvious  that  a  small  positive  must 
first  be  made  by  contact  printing  from  the  original  negative,  and 
then  the  enlarged  negative  from  this  in  the  usual  way.  The  best 
method  of  making  the  small  negative  is  a  matter  of  dispute,  some 
preferring  the  carbon  process,  others  the  ordinary  lantern  or 
gelatino-bromide  or  chloride  plate.  The  latter  plan  will  certainly 
be  found  the  more  convenient  for  amateur  workers.  The  small 
positive  may  be  made  on  any  lantern  plate  and  developed  with 
any  developer.  Care  should  be  taken  to  make  it  as  perfect  as 
possible,  and  all  small  imperfections,  etc.,  should  be  retouched  or 
spotted  out  on  the  positive.  By  making  a  cloud  positive  on  a 
separate  slide,  and  using  it  as  a  cover  glass  like  a  lantern  slide, 
clouds  may  be  obtained  in  the  enlarged  negative.  The  enlarged 
negative  may,  of  course,  be  developed  with  any  developing  agents  ; 
but  in  this,  as  when  developing  the  small  positive,  care  should 
be  taken  to  keep  the  whole  rather  thin,  a  delicate,  full-of-detail 
negative  and  positive,  giving  the  best  results.  The  large  negative 
may  also  obviously  be  made  by  using  a  negative  in  the  first 
instance,  and  obtaining  a  positive  by  enlargement,  and  then 

179 


Eos] 


DICTIONARY  OF  PHOTOGRAPHY. 


obtaining  a  negative  from  this  by  contact  printing.  Celluloid 
coated  with  gelatino-bromide  emulsion  may  also  be  obtained 
commercially  ;  and  this  may  be  utilised  either  for  positives,  trans- 
parencies, or  negatives,  the  necessary  treatment  being  precisely 
the  same  as  indicated  above,  for  paper,  opals,  or  plates,  according 
to  the  method  of  viewing  the  same  for  which  the  enlargement  is 
required. 

Eosin  (Ger.,  Eosin ;  Fr.,  Eosine ;  Ital.,  Eosina).  A  generic 
name  given  to  various  colouring  matters  obtained  from  fluorescine, 
which  have  been  used  in  ortho-chromatic  work. 

Equivalent  Focus.   See  Focus. 

Erythrosine  (Ger.,  Erythrosin ;  Fr.,  Erythrosin ;  Ital., 
Eritrosind).  C20H6I4O5K2.  Synonym :  Tetraiodofluorescine  of 
Potassium.  This  is  a  derivation  of  fluorescine,  and  closely  allied 
to  eosine.    It  is  used  in  orthochromatic  photography. 

Ether  (Ger.,  Schwefelaether ;  Fr.,  Ether;  Ital.,  Etere). 
C4H]0O  =  74.  Synonym  :  Sulphuric  Ether.  A  volatile,  inflam- 
mable, colourless  liquid,  prepared  from  alcohol  by  distillation  with 
sulphuric  acid,  and  subsequent  purification.  It  has  a  peculiar, 
strong,  sweet  odour,  and  a  hot,  burning  taste,  evaporating  quickly 
on  exposure  to  the  air,  and  when  applied  to  the  skin  leaving  a 
feeling  of  considerable  coldness.  It  boils  below  1050  F.,  and 
gives  off  at  ordinary  temperatures  a  heavy,  inflammable  vapour. 
Water  takes  up  about  one-tenth  of  its  volume  of  ether,  and  vice 
versa  ;  should  it  absorb  more,  it  proves  the  presence  of  too  much 
alcohol.  It  unites  in  all  proportions  with  alcohol.  Specific 
gravity  should  be  about  735.  It  is  a  solvent  of  all  fixed  and 
essential  oils,  iodine,  bromine,  and  sparingly  of  sulphur  and 
phosphorous.  It  dissolves  most  resins  and  balsams,  also  india- 
rubber  and  caoutchouc.  It  contains  about  8  per  cent,  of 
alcohol. 

Pure  or  Absolute  Ether  is  prepared  from  above  by  shaking  it 
with  half  its  weight  of  distilled  water,  which  dissolves  the  8  per 
cent,  of  alcohol,  and  decanting  the  supernatant  ether  and  dis- 
tilling it  with  chloride  of  calcium,  which  extracts  the  small 
amount  of  water  absorbed  by  the  ether.    Specific  gravity,  720. 

Methylated  Ether  is  prepared  precisely  as  above,  but  from 
180 


DICTIONARY  OF  PHOTOGRAPHY.  [Exp 

methylated  spirit.  It  is,  if  pure  and  free  from  methyl,  quite  as 
satisfactory  for  the  preparation  of  collodion  as  that  from  rectified 
spirit.  To  test  whether  a  sample  be  suitable  for  preparing 
collodion,  put  one  drop  of  tincture  of  iodine  into  an  ounce  of 
methylated  ether,  and  expose  to  daylight.  If  the  colour  is 
discharged  after  a  few  hours,  the  sample  should  be  rejected. 
Ether,  whether  prepared  from  rectified  or  methylated  spirit,  is 
liable  to  become  ozonised,  or  acid,  by  exposure  to  light,  in  which 
condition  it  is  unfit  for  the  preparation  of  collodion.  This  state 
can  be  tested  for  by  agitating  it  with  an  alcoholic  solution  of 
iodide  of  potassium.  When  acid,  the  iodine  is  liberated,  and 
the  solution  is  coloured  the  characteristic  yellow  colour  of  free 
iodine. 

Exposure.  Placing  any  sensitive  surface  under  the  action  of 
light,  either  in  the  camera  or  in  a  printing  frame.  Of  the  latter 
but  little  need  be  said,  as  the  result  is,  in  the  case  of  sensitised 
paper,  visible  ;  and  in  the  case  of  bromide  and  other  papers  and 
opals  for  development  instructions  will  be  found  under  those 
headings.  Of  the  former  but  little  can  be  said  here  ;  whole 
volumes  might  beiwritten  without  affording  much  material  aid. 
We  may  well  divide  the  factors  which  influence  the  duration  of 
exposure  into  five  distinct  points  :  (i)  Light,  (2)  Plate,  (3)  Subject, 
(4)  Diaphragm,  (5)  Distance. 

(1)  Lighi.  In  estimating  the  quality  of  the  light  which  falls 
upon  the  subject,  we  have  several  points  to  take  into  considera- 
tion. It  has  been  and  still  is  the  accredited  custom  of  many 
operators  to  judge  of  the  quality  of  the  light  by  the  image  as 
seen  on  the  focussing  screen  ;  that  is  to  say,  many  operators 
still  employ  the  method  of  calculating  exposure  by  means  of  the 
optical  brightness  of  the  light,  and  not  by  the  chemical  bright- 
ness— two  totally  distinct  properties  of  light,  between  which 
there  is  not,  unfortunately,  any  fixed  ratio  or  connection.  Other 
important  factors  in  determining  the  quality  of  the  light  are, 
climatic  or  meteorological  circumstances,  the  latitude  of  the 
place,  and  the  height  of  the  object  above  the  level  of  the  sea, 
this  last  only  being  taken  into  account  when  on  mountains,  etc. 
It  will  be  almost  impossible  for  me  to  give  full  and  complete 
information,  but  as  far  as  possible  within  reasonable  limits  I 
shall  do  so.    Dr,  Holetschek,  of  Vienna,  has  reckoned  for  Vienna 

i8x 


Exp] 


DICTIONARY  OF  PHOTOGRAPHY. 


and  all  places  of  that  latitude  the  chemical  light  intensity  of 
sunlight  and  that  of  a  blue  sky  (see  Appendix),  and  Dr.  Spitaler 
has  given  one  for  different  degrees  of  latitude.  The  difference 
in  chemical  intensity  of  the  light  in  the  course  of  a  day  is  another 
point,  and  theory  as  well  as  practice  has  proved  that  the  most 
intense  light  is  on  a  cloudless  sunny  day  about  II  to  12  in  the 
morning ;  after  noon  the  intensity  sinks,  because  the  heat  of  the 
sun  has  filled  the  air  with  aqueous  vapour  and  the  sun  itself  has 
begun  to  sink,  and  therefore  its  light,  passing  through  a  greater 
and  ever-increasing  thickness  of  atmosphere,  loses  in  a  marked 
manner  its  chemical  activity,  which  resides,  as  we  have  already 
seen,  in  the  blue  and  violet  rays,  which  are  more  quickly,  and  in 
greater  proportion,  absorbed  than  the  less  refrangible  rays. 
Professor  Langley  (Washington,  1884)  has  given  the  following 
results  of  the  experiments  carried  out  by  him,  as  to  the  absorption 
of  the  different  rays  of  the  spectrum. 

Ultra  violet  rays  absorbed,  61%  ;  allowed  to  pass,  39%. 


From  this  it  is  obvious  that  the  greater  the  thickness  of  atmo- 
sphere through  which  the  sun's  rays  have  to  pass,  the  greater 
the  absorption  of  the  chemical  or  more  refrangible  rays.  The 
chemical  power  of  the  sun's  light  is,  moreover,  dependent  on 
the  absence  or  presence  of  dust,  the  height  of  the  barometer,  etc. 
Again,  the  wind  has  some  influence,  because  when  a  dry  north- 
east or  east  wind  prevails,  and  prevents  the  condensation,  or 
rather  the  increase,  of  the  aqueous  vapour,  the  chemical  intensity 
of  the  light  will  increase  ;  on  the  other  hand,  when  a  wet  south- 
west or  west  wind  prevails,  the  increase  of  the  aqueous  vapour 
will  lower  the  intensity.  Clouds,  we  all  know,  play  an  important 
part  in  determining  the  duration  of  exposures,  but  there  are 
clouds  and  clouds.  Thin  haze  or  mist,  such  known  as  "  heat 
mist,"  lowers  the  chemical  power  enormously ;  yet  optically 
there  is  little  difference.  The  fine  white  masses  of  clouds  float- 
ing in  a  blue  sky  rather  increase  than  decrease  the  power  of  the 


Greenish  blue 

Yellow 

Red 

Infra  red 


Violet 
Blue 


58% 
52% 
46% 
37% 
3o% 
24% 


42%. 
48%. 
54%. 
63%. 
7o%. 
76%. 


182 


DICTIONARY  OF  PHOTOGRAPHY. 


[Exp 


light,  in  that  they  act  as  enormous  reflectors  of  the  sun's  light. 
Generally,  however,  when  the  sky  is  cloudy  and  the  sun  not 
actually  shining,  the  exposure  is  about  three  times  that  with  the 
sun  out ;  with  a  dull  leaden  pall  of  cloud  the  chemical  intensity 
of  the  light  may  be  reduced  to  one-fourth  or  one-eighth,  or  even 
more. 

(2)  The  Plate.  The  sensitiveness  of  the  plate  used  is  another 
important  factor,  and  is  treated  of  under  Sensitiveness  (q.v.). 

(3)  The  Subject.  This  is  one  of  the  factors  much  misunder- 
stood. Experience  soon  teaches  the  novice  that  a  short  exposure 
is  required  for  a  white  object,  more  for  a  dark-coloured ;  but  few 
recognise  that  darkness  in  colour  or  tone  is  not  the  same  thing 
as  darkness  in  lighting,  and  that  a  white  object  badly  lit  may 
require  more  exposure  than  a  dark  object  well  lit.  We  may 
well  here,  I  think,  note  the  point  of  subject  colour  with  regard 
to  colour  sensitiveness.  If  we  have  to  copy,  for  instance,  a 
yellowish  object,  and  use  an  ordinary  plate  which  is  not  sensitive 
to  yellow,  we  must  give  a  much  longer  exposure  than  when 
using  a  plate  which  has  been  "  colour  sensitised  "  for  yellow,  if 
we  wish  "to  show  correctly  the  difference  in  the  lightness  or 
darkness  of  objects." 

(4)  The  Diaphragm.  The  influence  of  the  diaphragm  or  stop 
on  exposure  we  have  already  noted.    See  Diaphragm. 

( 5)  Distance.  The  more  distant  an  object  is  from  the  lens, 
the  less  the  exposure,  other  conditions  remaining  the  same. 
This  is  the  generally  accepted  rule,  but  it  is  extremely  doubtful 
whether  any  actual  experiments  have  been  carried  out  on  this 
point.  Mr.  Watkins,  in  his  little  pamphlet  "  Notes  on  Exposure," 
says  on  this  subject:  "It  maybe  taken  as  a  general  rule  that, 
except  when  photographing  near  objects  (less  than  twenty-four 
times  the  focus  of  the  lens  distant),  or,  on  the  other  hand, 
extreme  distances  in  landscape,  no  variation  need  be  made  for 
differences  in  distance.  When  a  very  near  object  is  photographed, 
the  camera  has  to  be  racked  out,  and  the  exposure  increases  in 
proportion  to  the  square  of  the  increased  focus  of  the  lens. 
When  the  subject  is  more  than  twenty-four  times  the  focus  of 
the  lens  distant  (18  feet  for  a  9-in.  lens)  this  variation  is  too 
minute  to  be  taken  into  account,  and  if  the  air  were  perfectly 
clear — as  it  is  sometimes  among  the  Swiss  peaks — all  objects 
beyond  that  distance  would  require  the  same  exposure.  In 

183 


Exp] 


DICTIONARY  OF  PHOTOGRAPHY. 


England,  however,  the  slight  fog  or  mist  almost  always  present 
in  the  air  adds  reflected  light  to  objects  more  than  one  or  two 
hundred  yards  distant,  and  thus  decreases  the  exposure  (it  is 
impossible  to  express  this  by  rule,  as  it  depends  entirely  upon 
the  amount  of  mist  in  the  air)."  To  the  best  of  my  ability, 
without  unduly  increasing  the  bulk  of  this  article,  I  have  con- 
sidered the  factors  regulating  exposure,  and  shall  conclude  by 
describing  as  far  as  I  can  the  various  instruments  and  tables 
used  by  photographers  for  the  same  purpose. 

Hurter  and  Driffield's  Actinograph,  see  Actinograph. 

Green  and  Fuidge's  Actinometer.  This  presents  the  appear- 
ance of  a  small  box  about  the  size  of  a  watch,  on  the  cover  of 
which  are  painted  seven  tints,  each  successive  tint  increasing  in 
depth  of  colour,  the  same  being  fac-similes  of  the  colour  from 
its  lightest  to  its  deepest  shade  produced  by  printing  on  sensitive 
albumenised  paper.  Fuller  descriptions  of  this  must  be  obtained 
from  the  makers.  The  instrument  assumes  that  the  colour 
obtained  by  printing  on  albumenised  paper  is  always  the  same  ; 
that  is  to  say,  that  all  albumenised  papers  will  print  to  the  same 
tint,  an  assumption  by  no  means  borne  out  by  my  experience. 
Moreover  it  will  be  acknowledged  by  most  of  my  readers  that  the 
ratio  between  the  formation  of  a  coloured  reduction  product  on 
a  complex  mixture  of  silver  salts,  as  is  present  on  ordinary 
sensitised  albumenised  paper,  and  the  formation  of  the  invisible 
image  on  bromide  or  bromo-iodide  of  silver  is  by  no  means 
constant,  nor  are  the  two  sensitive  to  the  same  particular  parts 
of  the  spectrum. 

Reid's  Actinometer  somewhat  resembles  in  appearance  a 
pocket  comb,  and  depends  upon  the  same  principle  as  Green 
and  Fuidge's  actinometer,  and  is  open  to  the  same  objections. 

Watts  Bijou  Actinometer.  Based  on  exactly  the  same 
principle  as  the  two  previous  ones. 

Stanley's  Actinometer.  This  consists  of  a  reel  of  paper, 
coated  with  a  gelatino-bromide  emulsion  which  has  been  treated 
with  a  10  per  cent,  solution  of  nitrite  of  potassium,  which  causes 
a  distinct  coloration  by  the  action  of  light. 

IVatkins'  Exposure  Meter.  This  consists  of  a  brass  cylinder 
with  movable  pointers  and  scales.  At  one  end  is  an  actinometer 
of  bromide  of  silver  paper,  which  is  exposed  to  the  light  which 
falls  upon  the  subject,  whilst  the  other  end  of  the  cylinder  is 

184 


DICTIONARY  OF  PHOTOGRAPHY. 


[Exp 


unfastened  and  set  swinging,  each  swing  beating  half  seconds. 
One  of  the  pointers  is  set  to  the  number  of  seconds,  and  the 
other  pointers  are  set  to  the  various  factors  of  plate  number, 
subject  number,  and  diaphragm,  when  the  last  pointer,  will 
indicate  the  exposure  required.  A  great  improvement  has  lately 
been  introduced  into  this  instrument  in  the  shape  of  a  small 
circle  of  pale  blue  glass,  covering  the  bromide  paper  which 
renders  the  matching  of  the  standard  tint,  previously  a  difficulty 
sometimes  met  with,  very  easy. 

Optical  Photometers.  Under  this  heading  we  include  instru- 
ments which  are  used  to  estimate  optically  the  exposure  required 
for  any  given  subject,  and  as  they  differ  slightly  in  use,  we  give 
a  note  on  each,  with  the  remark  that  it  is  utterly  absurd,  as  we 
have  already  pointed  out,  to  try  to  estimate  the  photographic 
intensity  of  the  light  by  optical  brightness. 

Decoitduris  Photometer.  This  instrument  consists  practically 
of  a  small  brass  circular  box  containing  sheets  of  tissue  paper 
in  increasing  thickness,  and  it  was  introduced  commercially  in 
1888.  The  method  of  using  this  instrument  is  as  follows  : — The 
instrument  is  held  with  the  right  hand  on  the  ground-glass  of  the 
camera,  whilst  the  focussing  cloth  must  be  carefully  wrapped 
round  the  operator's  head,  so  as  to  exclude  any  light  but  that 
passing  through  the  ground-glass.  The  operator  now  observes 
from  the  distance  of  normal  vision  the  small  aperture  to  the  left 
of  the  photometer,  where  three  small  holes  and  one  large  one 
are  seen.  The  milled  head  in  the  centre  of  the  instrument  is  now 
turned  till  the  three  small  holes  are  no  longer  visible,  and  the 
instrument  is  then  removed,  turned  over,  and  a  letter  will  be 
observed,  which  gives  an  index  of  the  exposure  required,  as 
against  the  letter  in  the  table  of  the  instrument  will  be  found  the 
exposure.  Weber  ("  Phot.  Mittheil.",  vol.  xxv.,  p.  37)  has  pointed 
out  that  this  instrument  possesses  a  scale  of  brightness  of  9-48 
to  0-35,  to  which  the  exposure  is  theoretically  inversely  pro- 
portional— that  is  to  say,  the  time  of  exposure  should  be  from 
1  to  27 — whilst  Decoudun  gives  his  scale  of  exposures  from 
1  to  750,  which  is  quite  sufficient  to  condemn  it.  Goerz,  of  Berlin- 
Schoneberg,  has  introduced  an  improved  and  simplified  form, 
which,  however,  is  also  open  to  the  same  theoretical  objections. 

Tylar  and  Pkkard's  Exposure  Meter.  This  consists  of  a 
metal  tube,  the  interior  of  which  is  provided  with  holes  and 

185 


Exp] 


DICTIONARY  OF  PHOTOGRAPHY. 


increasing  thicknesses  of  a  translucent  material  which  are 
brought  before  the  holes  by  means  of  an  external  pointer,  which 
indicates  the  exposure  on  a  tablet  affixed  to  the  outside.  This 
is  open  to  the  same  objection  as  the  last  instrument,  but  differs 
from  it  in  that  it  is  directed  to  the  subject,  and  not  to  the  screen. 

Phosphorescent  Photometers.  There  are  only  two  such  in- 
struments on  the  market,  so  far  as  I  am  aware,  both  of  which 
depend  upon  the  exciting  of  phosphorescent  paint,  and  the  power 
of  the  paint  to  retain  and  throw  out  again  the  light  impressions. 

Warnerke's  Phosphorescent  Photo?neter.  The  principle  of  this 
is  the  excitation  of  a  patch  of  luminous  paint  by  the  light  falling 
upon  the  subject  for  one  second,  and  then  the  estimation  of  the 
brightness  of  the  luminescent  paint  by  means  of  translucent 
screens  of  increasing  thickness. 

Ballard's  Actinometer.  This  depends  for  its  action  on  the 
power  of  luminous  paint  to  retain  and  throw  out  again  the  light 
impressions  it  has  received,  and  it  consists  of  a  square  tube  of 
wood,  having  at  one  end  a  hinged  cover,  with,  on  the  inside,  a 
prepared  surface  and  a  spot  in  the  centre.  The  method  of  using 
is  to  open  the  cover,  and  look  through  the  tube  directly  at  the 
object  to  be  photographed  for  half  a  minute,  then  closing  the  tube, 
a  central  blue  spot  will  be  seen,  which  will  gradually  disappear. 
The  number  of  seconds  which  it  takes  to  do  this  forms  the  basis 
of  the  calculation  of  a  series  of  tables  which  accompany  the 
actinometer.  The  fault  of  these  instruments,  which  depend 
upon  phosphorescent  paint,  is  that  the  personal  equation  of  the 
individual  eye  comes  into  play,  and  that,  according  to  Wiedeman 
(Eder's  "  Jahrbuch,"  1891,  p.  588),  if  Balmain's  luminous  paint  be 
exposed  for  one  second,  the  brightness  of  the  light  emitted  from 
that  paint  is  not  constant,  as  shown  by  the  following  table  : — 

After  the  lapse  of    4  sees.,  brightness  =  27*8 

=  7-6 
=  4-2 
s  3-1 
=  1-9 


and  the  shorter  the  exposure  the  greater  the  sudden  drop,  and 
there  is  no  constant  ratio. 

186 


20 
40 
60 
90 
180 
240 


DICTIONARY  OF  PHOTOGRAPHY. 


[Exp 


The  Ilford  Exposure  Meter.  This  is  practically  a  circular 
slide  rule,  with  discs  which  can  be  revolved  and  set  to  the 
different  factors  of  plate,  stop,  time,  and  subject ;  the  exposure 
being  read  off  and  modified,  according  to  the  time  of  year,  from 
a  table  on  the  back  compiled  by  Dr.  Scott,  by  whom  the  instru- 
ment was  devised. 

Wynne's  Infallible  Exposure  Meter.  This  is  a  combination 
of  a  slide  rule  and  actinometer  of  silver  bromide  paper.  Having 
briefly  reviewed  the  commercial  exposure  meters,  actinometers, 
etc.,  and  stated  the  objections  to  their  use,  it  is  only  fair  I  should 
treat  the  tables  on  the  same  plan.  In  the  Appendix  will  be 
found  samples  of  most  of  the  published  tables  which  are  calcu- 
lated on  the  experience  and  record  of  past  years  ;  but  the  objec- 
tion to  these  tables  is  that  the  experience, or  results  obtained 
either  in  one  year  or  in  one  thousand  years  cannot  give  us  any 
clue  as  to  what  the  light  will  be  at  any  given  hour  of  any  given 
day  in  the  year.  But  whilst  exposure  meters,  actinometers,  and 
tables  are  not  strictly  accurate,  there  is  not  the  slightest  doubt 
that  they,  one  and  all,  are  of  more  or  less  assistance  to  beginners 
by  giving  some  idea  of  the  necessary  duration  of  exposure,  and 
will  therefore  prove  useful  in  forming  a  nearer  estimate  than  the 
inexperienced  and  untutored  mind. 

Counting  the  Time  of  Exposure.  Possessors  of  a  watch  with 
a  second  hand  will  have  no  difficulty  in  counting  the  duration 
of  a  lengthy  exposure,  but  for  shorter  periods  than  this  some 
other  aid  is  required.  Most  modern  watches  tick  five  times 
in  a  second,  occasionally  one  may  be  picked  up  which  ticks 
four  to  the  second  ;  there  are  also  cheap  stop-watches  on  the 
market,  which  can  be  obtained  from  most  pawnbrokers,  which 
have  an  extra  hand  marking  fifths  of  a  second,  and  which  can 
be  stopped  or  started  in  one-fifth  of  a  second.  The  writer  has 
one  which  he  bought  new  for  12s.  6d.,  which,  although  remark- 
ably erratic  as  a  timekeeper,  acts  well  for  timing  purposes.  It 
has  also  been  suggested  to  use  a  bunch  of  keys  or  a  bullet  tied 
to  a  string  9^  ins.  in  length,  which,  when  set  swinging,  beat 
half-seconds.  But  in  many  cases  it  is  desirable  to  look  at  the 
subject  whilst  making  an  exposure,  especially  when  such  is  of 
short  duration ;  it  then  becomes  impossible  to  look  at  a  watch 
or  swinging  body  at  the  same  time.  Therefore,  the  author  has 
for  some  considerable  time  practised  counting  seconds,  and  does 

187 


Fab] 


DICTIONARY  OF  PHOTOGRAPHY. 


so  now,  with  such  accuracy  that  in  three  trials  against  a  watch 
of  5,  10,  and  30  sees,  the  error  was  only  |,  £,  and  J  sec.  re- 
spectively. This  accuracy  can  only  be  obtained  by  practice,  but 
it  soon  becomes  easy.  The  writer's  method  of  counting  is  as 
follows  :  Say,  for  instance,  3  sees,  are  required.  Then,  as  soon  as 
the  cap  is  removed,  count  1,  2,  3,  4 ;  2,  2,  3,  4 ;  3,  2,  3,  4.  Again,  we 
will  suppose  i£  sec.  is  required,  1,  2,  3,  4;  2,  2.  It  will  be  seen 
from  this  that  four  are  counted  to  the  second,  and  each  second 
begins  with  number  which  the  four  when  counted  will  complete. 

Fabric,  Golden.  A  translucent  cloth  died  golden  or  yellow, 
used  for  the  dark-room  window.  It  should  always  be  tested  to 
see  whether  actinic  light  filters  through,  as  described  under 
Dark-Room  {q.v.).  A  convenient  and  ingenious  way,  suggested 
to  me  by  an  amateur  of  some  standing,  for  utilising  this  fabric  is 
as  follows  : — Make  a  frame  of  wood  sufficiently  large  to  cover 
the  window,  and  on  to  this  frame  paste  or  nail  a  sheet  of  fabric, 
smear  the  inside  of  sheet  all  over  with  vaseline,  and  squeegee 
another  sheet  of  fabric  to  it.  The  vaseline  fills  up  the  minute 
pores,  and  causes  the  two  sheets  to  adhere,  making  the  medium 
much  safer. 

Fading.  The  worst  of  all  ills  to  which  negatives  and  prints 
are  subject. 

Negative  fading.  This  is  solely  due  to  insufficient  washing 
or  fixing,  and  the  consequent  action  of  hypo  on  the  delicate 
image  of  silver. 

Fading  of  Prints.  The  cause  of  this  may  in  every  case  be 
traced  in  some  way  or  other  to  sulphur,  or  its  compounds. 
Albumen  itself  contains  a  minute  trace  of  sulphur,  and  conse- 
quent decomposition  may  give  rise  to  the  formation  of  some 
compound  of  sulphur  and  silver.  Again,  insufficient  fixing  may 
form  the  insoluble  variety  of  hyposulphite  of  silver,  and  in- 
sufficient elimination  of  the  fixing  salt  itself  may  supply  the 
unlooked-for  result.  Hypo  is  used  as  an  anti-chlor  in  the 
manufacture  of  some  mounts,  and  this  should  be  tested  for  as 
described  under  the  head  of  Sodium  Hyposulphite  (q.v.).  An 
acid  or  decomposing  mountant,  or  absorption  by  an  hygroscopic 
mount  of  the  aqueous  vapour  from  the  atmosphere  holding  in 
solution  certain  acids,  may  also  cause  it.  To  prevent  any  such 
action,  great  care  should  be  taken  to  completely  eliminate  the 

188 


DICTIONARY  OF  PHOTOGRAPHY. 


[Fee 


fixing  salts,  and  the  use  of  encaustic  paste  is  likewise  a  protection 
from  the  aqueous  vapour. 

Fahrenheit.   See  Thermometer. 

Falling  Front.   See  Rising  Front. 

Feer-type.    This  process  is  founded  on  the  property  pos- 
sessed by  diazo  compounds,  of  forming  diazo-sulphonic  salts 
with  sodium  sulphite  ;   and  these  diazo-sulphonic  compounds, 
when  mixed  with  phenol  or  amines  and  exposed  to  light,  are 
decomposed,  and  the  diazo  compound  is  set  free  and  forms  a 
colouring  matter — a  positive  is  thus  obtained  from  a  negative. 
This  process  was  patented  by  Dr.  Adolf  Feer  in  1889,  and  the 
following  is  a  translation  of  his  patent : — The  present  process 
rests  on  the  fact  that,  as  the  inventor  has  discovered,  diazo- 
sulphonic  salts  (R  -  N=N  -  S03Na)  react  with  phenol  alkalies 
and  hydrochloric  or  free  aromatic  amines,  under  the  influence 
of  solar  or  electric  light,  with  the  formation  of  the  azo  colouring 
matter.    To  carry  out  this  process  the  inventor  impregnates  paper 
or  cloth  with  a  diluted  molecular  mixture  of  a  diazo-sulphonic 
salt  {e.g.,  of  anilin,  amido  azo-benzol,  benzidine,  and  their  homo- 
logues)  and  phenol  alkalies  (e.g.,  phenol,  resorcin,  a-  and  /3- 
naphthol),  or  hydrochloric  or  free  amines  (anilin,  naphthylamin, 
phenylendiamin,  and  their  homologues)  ;  the  paper  or  mate  rial 
is  then  dried  in  the  dark,  and  exposed  under  a  negative  for  about 
five  minutes,  or  to  the  electric  light.    By  this  means  there  is 
formed  on  the  exposed  places  the  insoluble  azo  colouring  matter, 
whilst  on  the  unexposed  parts,  under  the  opaque  portions  of  the 
negative,  the  preparations  remain  in  their  original  conditions  of 
solubility  and  colourlessness.    The  picture  is  thus  developed. 
After  exposure  the  print  is  washed  with  water  or  very  dilute 
hydrochloric  acid,  by  which  means  the  unchanged  preparation, 
which  has  not  been  exposed  under  the  negative,  is  removed. 
The  print  is  then  fixed  and  finished  when  dry.    The  following 
may  be  taken  as  samples  of  solutions  : — 


1. 


Sodium  toluene-diazosulphonate  . 

/3-naphthol  ...   

Sodium  hydrate   

Water   


1000 


25  parts. 

25  M 
8  „ 


11 


189 


Fer] 


DICTIONARY  OF  PHOTOGRAPHY. 


II. 

Sodium  ditolyl-tetrazosulphonate  .. .       ...  25  parts. 

Metaphenylene-diamine    ...       ...       ...  20  ,, 

Water    1000  ,, 

III. 

Sodium  ditolyl-tetrazosulphonate   25  parts. 

Resorcinol    ...       ...       ...       ...       ...  12 

Sodium  hydrate    16  „ 

Water  ...       ••■    1000 

The  following  may  also  be  used : — 

IV. 

Sodium  ditolyl-tetrazosulphonate ...       ...  30  parts. 

Resorcinol                         ...       ...       ...  20  „ 

Sodium  hydrate      ...                            ...  15  „ 

Distilled  water    1000 

Finely  powder  all  the  salts  and  dissolve  in  the  water  by  the  aid 
of  a  gentle  heat. 

V. 

Sodium  ditolyl-tetrazosulphonate   30  parts. 

a-naphthol    ...       ...                            ...  25  „ 

Sodium  hydrate                           ...       ...  7  » 

Distilled  water    1000  ,, 

VI. 

Sodium  ditolyl-tetrazosulphonate ...       ...  30  parts. 

Phenylendiamin                           ...       ...  20  „ 

Distilled  water    1000  „ 

For  sensitising  the  paper  or  materials  solutions  IV.  and  V.  or  V. 
and  VI.  may  be  mixed  in  equal  parts.  The  paper  is  impregnated 
with  the  desired  mixture,  dried,  and  then  exposed  under  a  nega- 
tive for  ten  or  fifteen  minutes,  and  after  exposure  washed  in 
dilute  hydrochloric  acid,  and  finally  with  water  and  dried.  Feer 
has  lately  suggested  diazo-pseumocumidine  sulphonate,  and  this, 
with  /3-naphthol  and  sodium  hydrate,  gives  scarlet-red  images  ;  by 
replacing  the  /3-naphthol  with  o-naphthylamin  violet  images  are 
obtained,  and  by  using  resorcinol  orange  colours  are  obtained. 

Ferrotypes.  Positives  taken  by  the  wet  process  on  thin  iron 
plate,  which  is  coated  with  brown  or  black  varnish.    As  the  pro- 

190 


DICTIONARY  OF  PHOTOGRAPHY. 


[Fix 


duction  of  these  is  exactly  the  same  as  the  production  of  collodion 
positives  on  glass,  and  full  instructions  are  given  for  this  under  Wet 
Collodion  {q.v.),  it  will  not  be  necessary  to  repeat  the  same  here. 

Field  of  a  Lens  is  the  circle  of  light  given  by  the  lens,  the 
diameter  of  which  is  usually  expressed  in  degrees,  but,  as  we 
have  already  noted,  is  far  better  expressed  in  terms  of  the  focal 
length.  The  extent  of  surface  which  a  lens  will  cover  is  inde- 
pendent of  the  diameter  of  the  diaphragm  aperture,  but  the  area 
of  sharp  focus  is  in  proportion  to  the  said  diameter.  (See  also 
Angle  of  View.) 

Film.    The  thin  pellicle  or  skin  of  gelatine  on  plates  or  paper. 

To  Remove  Old  Films.  Nothing  is  better  than  glacial  acetic 
acid  made  into  a  cream  with  pumice-stone  powder  and  applied 
with  a  tuft  of  rag,  the  acid  instantly  dissolving  the  film,  and  the 
pumice  powder  acting  as  a  mechanical  means  of  removing  it. 

To  Clean  the  Film  from  the  Back  of  Plates.  Few  plate  manu- 
facturers coat  their  plates  so  carefully  but  what  some  small  smears 
of  emulsion  get  on  the  back  of  plate.  To  remove  this,  when  the 
plate  is  thoroughly  dry,  place  it  face  downwards  upon  a  pad  of 
blotting  paper,  and  use  a  little  salt  with  a  moistened  rag. 

Film  Photography.  The  disadvantages  of  glass  when  used 
as  a  support  for  the  sensitive  emulsion — which  are  its  weight,  its 
bulk,  and  liability  to  fracture — have  induced  many  experimenters 
to  search  for  a  light,  flexible  support  which  might  be  used  as  a 
substitute.  Thirty  years  ago  waxed  paper  was  used,  and  on  the 
introduction  of  gelatine  emulsions  the  search  for  a  substitute 
received  great  impetus.  Woodbury,  in  1 871,  suggested  Tollable 
films;  Warnerke,  in  1876,  used  gelatine  emulsion  spread  on 
paper,  from  which  it  was  afterwards  stripped  ;  Pumphrey, 
Vergara,  and  others  followed ;  but  it  was  not  till  the  introduction  of 
Celluloid  (q.v.)  that  a  satisfactory  stage  may  be  said  to  have  been 
reached.  The  treatment  of  films  is  exactly  the  same  as  for  glass 
plates,  and  therefore  no  special  instructions  need  be  included. 

Fixed  FOCUS. — This  term  has  become  so  general  of  late  that 
one  writer  actually  says,  "With  regard  to  fixed-focus  lenses  I  am 
quite  ignorant  of  the  principle  on  which  they  are  constructed, 
but  it  seems  to  me  a  most  extraordinary  thing,  if  they  can  be 
constructed  at  all,  why  any  other  kind  should  be  made.  With 

the  lens  on  my  everything  from  three  feet  to  the  extremest 

191 


Fix]  DICTIONARY  OF  PHOTOGRAPHY. 

distance  is  in  the  sharpest  possible  focus ;  and  this  being  so,  it 
is  most  amazing  that  makers  should  go  on  manufacturing  lenses 
that  require  re-focussing  for  every  picture,  which  is  in  all  cases  an 
unmitigated  nuisance  and,  in  the  case  of  instantaneous  pictures, 
the  cause  of  the  loss  of  more  than  half  the  chances  offered,  and 
of  half  the  pictures  actually  taken  being  out  of  focus."    It  is 
quite  possible  that  there  are  many  in  the  same  state  of  amaze- 
ment as  the  above  writer,  who  may,  for  all  I  know,  still  be  in 
the  same  state ;  therefore  to  him  and  to  others  like  him  it  may 
be  of  interest  to  learn  that  every  lens  has  a  fixed  focus,  and 
that  there  is  no  lens  which  is  manufactured  which   is  not 
quite  as  much  a  fixed-focus  lens  as  the  particular  lens  which 
called  forth  the  above  remarks,  and  that,  moreover,  there  never 
has  been  a  fixed-focus  lens  yet  made  and  never  will  be.  My 
readers  will  probably  say  that  I  have  been  dining,  or  something 
equally  flattering,  to  state  within  a  few  lines  that  every  lens  is 
a  fixed-focus  lens,  yet  that  such  a  lens  never  has  and  never  will 
be  made.    But  what  I  mean  to  state  is  this — a  fixed  focus  is 
a  theoretical  impossibility,  but  with  every  lens  there  is  a  point 
beyond  which  objects  are  in  sufficient  sharpness  to  satisfy  our 
requirements  as  to  definition,  because  when  the  image  of  a  point 
is  less  than  the  i^th  part  of  an  inch  in  diameter,  then  the  eye 
perceives  the  image  as  a  point  sharply  defined,  and  this  has 
given  rise  to  the  term  in  question.    Several  rules  are  in  existence 
for  finding  out  the  nearest  point  in  focus,  but  one  of  the  best 
is  that  by  Mr.  W.  Cheyney,  in  the  "Journal  of  the  Franklin 
Institute,"  which  is  as  follows: — Multiply  the  diameter  of  the 
aperture  of  a  lens  by  the  equivalent  focus  thereof,  divide  the 
product  by  the  greatest  allowable  error,  and  to  the  quotient  add 
the  equivalent  focus.    The  sum  will  be  the  distance  of  an  object 
upon  which  the  lens  should  be  accurately  focussed  in  order  that 
all  objects  beyond  a  point  one-half  of  the  above  distances  shall 
be  apparently  in  focus.    Thus — 

Let    f  =  the  equivalent  focus. 

a  =  the  diameter  of  aperture. 
e  =  the  greatest  allowable  error. 
Then  d  =  the  distance  of  an  object,  upon  which  if  the  lens  be 
accurately  focussed,  all  objects  beyond  d/2  will 
apparently  be  in  focus. 

192 


DICTIONARY  OF  PHOTOGRAPHY.  [Fix 

Or, 

d     X  f 

— +  f  =  d,  then  d      2  =  point  in  focus. 

Examples  .-—Thus  with  a  lens  of  8-in.  focus  and  //8  diaphragm 
we  have 

1x8 

— - —  +  8  =  d  =  2,008  in.  =  167  ft.  4  in. 

Then  d  -f-  2,  or  167  ft.  4-in,      2  =  83  ft.  8  in. 
Again,  if  we  use  a  lens  of  4-in.  focus  and  y/16  aperture  we  have 
—  x  4. 

4  .      +  4  =  d  =  254  in.  =  21  ft.  2  in. 

Then  d  ~  2  or  21  ft.  2  in. -4- 2  =  10  ft.  7  in. 
Mr.  Cheyney  gives  the  following  table  tested  by  various  rectili- 
near, wide-angle,  and  single  landscape  lenses  :  — 


Equiv. 

Aperture. 

Distance  of  Object 

All  Objects  in 

Focus. 

Focusseu  Upon. 

Focus  Beyond. 

2  • 

m 

IO  ft. 

7 

in. 

5ft. 

3  in. 

2 

7  N 

1 1 

II 

3  " 

11  n 

2 

//16 

5  M 

4 

2  ,, 

8  „ 

3 

//8 

23  n 

8 

11 

1 1  „ 

i°  11 

3 

//"•3i 

17  M 

10 

8  „ 

I  I  M 

3 

//16 

II  M 

1 1 

II 

5  .. 

I  I  11 

4 

//« 

42  „ 

0 

21  ,, 

O  ,, 

4 

y/n-31 

31  „ 

3 

15  ,. 

7  M 

4 

//16 

21  „ 

2 

1 

IO  M 

7  ., 

5 

//* 

65  „ 

6 

II 

32  n 

9  .. 

5 

y/n-3i 

49  m 

3 

24  M 

7  ,1 

5 

//16 

32  „ 

1 1 

ll 

16  „ 

5  M 

6 

94  „ 

3 

47  u 

1  ,1 

6 

//1131 

7o  „ 

9 

35  11 

4  11 

6 

//16 

47  11 

4 

23  „ 

8  „ 

7 

//8 

126  ,, 

1 

63  M 

0 

7 

7/II-3I 

94  „ 

8 

11 

47  H 

4  „ 

■  7 

//16 

63  M 

4 

H 

3i  M 

8  „ 

8 

//8 

167  1, 

4 

H 

83  „ 

8  „ 

8 

Z/n-31 

125  |, 

8 

62  „ 

10 

8 

//16 

84  „ 

0 

II 

42  „ 

0  || 

I  have  struck  out  fractions  of  an  inch  as  unnecessary.  On 

193  O 


Fix] 


DICTIONARY  OF  PHOTOGRAPHY. 


reading  through  the  above  table  many  of  my  readers  will  at  once 
exclaim,  "  If  this  is  right,  Messrs.  Blank  and  Blank,  lens  makers 
or  lens  sellers,  are  wrong  when  they  state  that  all  objects  beyond 
so  many  feet  will  be  in  focus  with  their  lens ;  their  distances  are 
not  nearly  so  much  as  the  above  table.  Take,  for  instance, 
Mr.  Dealer's  special  hand-camera:  this  has  a  5-in.  focus  lens, 
and  works  at //8,  and  yet  he  states  that  everything  beyond  15  ft. 
is  in  focus :  by  the  above  table  everything  beyond  32  ft.  is  in 
focus."  To  reconcile  these  seeming  paradoxes  is  not  difficult, 
as  it  will  be  noted  that  Mr.  Cheyney  takes  ^  of  an  inch  as 
the  greatest  permissible  error ;  if,  however,  we  take  T£7  of  an 
inch  as  the  permissible  error  we  get  totally  different  results,  as 
seen  by  working  out  his  examples : — 

L*_5  +  8  =  8o8  in  =  6?.4  ft> 

TT)"!! 

Then  67-4      2  =  33  ft.  8  in. 

And  t*i  +  4  =  104  =  8  ft.  8  in. 

Then  8  ft.  8  in.      2  =  4  ft.  4  in. 
Taking  T^  of  an  inch  as  the  permissible  error,  I  have  worked 
out  from  Mr.  Cheyney's  rule,  the  following  table,  which  may  be 
useful : — 


Point  Beyond  which  All  Objects  will  be  in  Focus. 


Apertures. 


//8. 


//16. 


4ft. 

6  „ 

8  „ 

10  ,, 

13  >i 

16  „ 

19  » 

22  ,, 

26  „ 


9  in. 

6  „ 

6  „ 

9  .» 

3  >l 

o  „ 

o  „ 

6  H 

o  ,, 


3 
4 

6 
8 

9 
1 1 

15 
16 
20 


6  in. 

9  » 

3  tf 

10  „ 

9  r, 

9  H 

o  „ 

6  H 

o  ,, 


2  ft. 

3  » 

4  t> 

5  if 

6  „ 

8  n 

9  M 
11  M 
13  » 


6  in. 
3 
3  ,f 
6  „ 
6  „ 
o 
6 

3 
o 


194 


DICTIONARY  OF  PHOTOGRAPHY. 


[Fix 


Another  rule  for  finding  the  same  is  : — Multiply  27  by  the  square 
of  the  focal  length  of  the  lens  and  by  the  fraction  expressing  the 
diameter  of  the  diaphragm  aperture. 

Example: — Required  the  nearest  point  in  focus  with  a  lens 
4^-in.  focus, //io  diaphragm. 

27  X  \\  X  4£  x  TV  =  27  x  20-25  x  -i  =  5-46  yards. 

Fixing.  The  removal  of  any  sensitive  salt  unacted  upon  by 
light  or  by  the  developer,  thus  rendering  the  negative  or  print 
unalterable  by  the  further  action  of  light.  The  usual  method  of 
effecting  this  in  the  case  of  the  silver  salts  is  by  the  solvent 
action  of  Hyposulphite  or  Thiosulphate  of  Sodium  (q.v.)  ;  cyanide 
of  potassium,  sulphocyanide  of  potassium  or  ammonium,  and 
sulphite  of  sodium  have  also  been  recommended.  Neither 
sulphocyanide  of  potassium  or  ammonium,  nor  sulphite  of  soda 
are  likely  to  come  into  general  use,  as  their  fixing  powers  are  not 
so  good  as  those  of  hypo,  and  their  price  is  greater.  Cyanide  of 
potassium  is  more  powerful  than  hypo,  but  its  action  on  the 
image  is  so  great  as  to  completely  destroy  the  half-tones  occa- 
sionally ;  its  use  should  never  be  countenanced  for  dry  plates  or 
prints.  Hypo,  then,  is  our  sole  resource ;  and,  whilst  it  is  much 
abused,  there  is  no  doubt  of  its  being  at  present  the  best  salt 
for  the  purpose.  The  difficulty  of  completely  eliminating,  how  - 
ever, is  its  great  drawback,  and  this  will  be  treated  of  under 
Washing  Negatives  and  Prints  {q.v.).  For  lixing  negatives  the 
author  recommends  the  use  of  two  fixing  baths,  the  strength 
being  about  4  ozs.  to  the  pint  of  water  in  each,  the  negative  being 
allowed  to  remain  for  ten  minutes  in  the  first,  and  for  about  five 
minutes  in  the  second  ;  by  this  a  more  thorough  fixing  of  the 
negative  is  effected.  For  fixing  prints  the  strength  generally 
recommended  is  about  half  that  for  negatives — that  is,  about 
2  ozs.  to  the  pint — and  sufficient  liquor  ammonia  or  carbonate  of 
ammonia  should  be  added  to  make  the  solution  smell  faintly  of 
ammonia.  This  neutralises  any  free  acid  which  may  be  present 
in  the  solution,  and  prevents  any  loss  of  tone  in  fixing.  The 
author  always  uses,  however,  the  same  strength  as  for  negatives, 
with  the  addition  of  ammonia,  and  uses  the  bath  at  a  tempera- 
ture of  700  F.  ;  and,  from  some  lengthened  experience,  the  results 
prove  the  increased  advantage  of  doing  this,  as  the  fixing  is  com- 

195 


Fla] 


DICTIONARY  OF  PHOTOGRAPHY. 


pleted  in  half  the  time,  and  there  is  less  chance  of  loss  of  tone. 
R.  E.  Liesegang  has  suggested  the  use  of  Thiosinamine  {q.v.)  as 
a  fixing  agent,  and  it  is  specially  adapted  for  prints.  For  plates 
its  action  is  much  slower  than  hypo,  but  it  is  said  to  possess  the 
advantage  of  being  more  quickly  removed.  The  strength  sug- 
gested is  i  per  cent. 

Flare.  A  fogged  central  patch  on  a  developed  plate,  or  seen  as 
a  circular  patch  of  light  on  the  focussing  screen.  It  is  said  to  be 
an  image  of  the  aperture  of  the  diaphragm,  or  in  some  cases  of 
the  lens  itself.  The  surface  of  the  lens  reflects  the  opening  of 
the  diaphragm  and  forms  a  distinct  image  of  it,  and  when  this 
coincides  with  the  focus  of  the  lens  this  image  is  seen  as  a 
flare  spot.  Again,  others,  and  amongst  them  Monckhoven,  in  his 
"  Photographic  Optics,"  states  that  it  is  due  to  too  close  an 
adherence  to  the  globular  form  by  the  optician  who  constructed 
the  lens.  Others,  again,  state  that  it  is  due  to  the  edges  of  the 
diaphragm  aperture  being  worn  bright,  and  this  no  doubt  is  a 
general  cause  for  its  sudden  appearance  in  a  lens.  The  Iris 
diaphragm,  but  lately  introduced  for  photographic  objectives, 
seems  to  be  particularly  liable  to  this,  from  the  friction  of  the 
tongues  of  metal  of  which  it  is  formed  ;  others  state  that  when 
the  lenses  are  mounted  in  cells  which  are  not  blackened,  a  flare 
is  almost  certain  to  make  its  appearance.  All  lenses  should  be 
examined  for  this  most  annoying  effect,  which  can  rarely  be 
wholly  eradicated.  It  is  very  often  a  defect  in  portrait  lenses 
when  such  are  used  for  outdoor  work  where  any  portion  of 
bright  sky  is  included  in  the  background,  and  in  this  instance  it 
is  clearly  an  image  of  the  lens  by  reflection  from  the  surfaces. 
The  remedies  are  not  by  any  means  satisfactory,  as,  whatever  is 
done,  at  its  best  the  flare  spot  is  so  distributed  over  the  whole 
plate  instead  of  being  localised.  When  the  diaphragm  edges  are 
worn  bright  they  should  be  blackened,  and  the  cells  in  which 
the  lenses  are  mounted  should  also  be  attended  to.  It  can  be 
eliminated  partially  as  stated  above,  by  altering  the  position  of 
the  diaphragm  slightly  ;  but  as  this  is  used  to  reduce  distortion 
to  a  minimum,  the  remedy  may  be  worse  than  the  disease  by 
introducing  this  defect.  Slightly  altering  the  relative  positions 
of  the  two  lenses  will  also  efface  it,  but,  as  said  before,  only  by 
distributing  it. 

196 


DICTIONARY  OF  PHOTOGRAPHY.  [FOC 

Flatness.  A  want  of  vigour  and  contrast  in  the  negative  and 
resulting  prints,  due  to  over-exposure,  or  to  the  use  of  too  strong 
or  too  weak  a  developer. 

Fluorhydric,  or  Hydrofluoric  Acid.  HF=i92.  Is  obtained 
by  heating  fluor-spar  with  sulphuric  acid  in  a  leaden  or  platinum 
retort,  connected  with  a  receiver  of  the  same  metal.  It  is  a 
colourless  gas,  very  soluble  in  water,  and  condensing  at  20  °  C. 
into  a  mobile  fuming  liquid,  which  boils  at  59 0  F.  It  has 
the  peculiar  property  of  dissolving  glass  and  other  silicates, 
and  for  this  reason  leaden  or  platinum  vessels  are  used  to 
prepare  it,  and  the  aqueous  solution  is  stored  in  india-rubber 
bottles.  Extreme  care  is  necessary  in  handling  it,  as  even  when 
dilute  it  causes  very  painful  ulcers  when  applied  to  the  skin,  and 
dissolves  the  nails. 

Fluorine.  F=  191.  A  non-metallic  element  never  met  with 
in  a  free  state,  and  usually  obtained  from  fluor-spar,  a  fluoride 
of  calcium,  CaF2.  It  is  of  little  practical  photographic  use ;  but 
its  compound,  hydrofluoric  acid,  has  been  recommended  for 
detaching  the  negative  film  from  glass  plates,  for  preparing  a 
film  negative.  (See  Stripping  Film.)  Fluorine  has  only  recently 
been  isolated 

Focal  Length,  Focus,  or  Equivalent  Focus.  A  term  ap- 
plied to  a  compound  or  doublet  lens.  It  is  the  focus  of 
parallel  rays  entering  the  lens,  and  is  thus  called  from  the  fact 
of  an  image  formed  at  that  point  equalling  in  size  that  formed 
by  a  single  lens.  It  is  extremely  important  that  every  photo- 
grapher should  know  how  to  find  the  focal  length  of  his  lens, 
because  upon  this  depends  the  determination  of  several  factors. 
Before  deciding,  however,  on  the  best  method  of  measuring  the 
focal  length,  it  is  necessary  to  know  where  we  are  to  start 
measuring  from.  If  we  take  a  single  or  landscape  lens  we  shall 
find  that  there  are  three  or  four  points  which  we  can  measure 
from.  Thus  we  may  measure  from  the  plane  of  the  diaphragm, 
from  the  front  surface  of  the  lens,  or  from  the  centre  of  the  lens, 
or  from  the  posterior  surface  of  the  lens ;  and  each  point  will 
give  us  a  different  length.  Thus  in  the  case  of  a  rectilinear  lens 
we  can  measure  from  several  points  :  from  the  front  lens,  from 
the  plane  of  the  diaphragm,  from  the  back  surface  of  the  posterior 

197 


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DICTIONARY  OF  PHOTOGRAPHY. 


lens.  It  is  very  usual  to  see  in  some  opticians'  catalogues  the 
term  "  back  focus,"  and  this  is  the  distance  between  the  posterior 
lens  and  ground-glass  ;  and  is,  I  believe,  inserted  for  the  infor- 
mation of  professional  photographers,  to  enable  them  to  judge 
whether  the  lens  can  be  used  on  their  cameras.  The  correct 
point  to  measure  the  focal  length  from  is  one  of  the  "  nodal 
points  "  of  a  lens,  but,  practically,  the  following  methods  may  be 
used  with  the  satisfaction  of  knowing  that  the  focal  length  of  any 
lens  thus  measured  is  sufficiently  accurate  for  all  practical  pur- 
poses. For  practical  purposes  it  is  quite  sufficient  to  set  the 
camera  up  and  focus  the  sun  or  the  clouds,  and  in  the  cases  of 
single  lenses  measure  the  distance  between  the  front  surface  of 
the  lens  and  ground-glass,  and  with  portrait  or  doublet  lenses  the 
distance  between  the  diaphragm  slot  and  ground-glass.  This 
method  is  not  precise,  however ;  more  accurate  measurements 
may  be  made  by  one  of  the  following  plans : — 

(i)  GrubUs  Method.  On  the  ground-glass  of  the  camera  draw 
two  pencil  lines  about  an  inch  from  the  margin  at  each  side. 
Now  set  up  the  camera  before  a  window,  preferably  upon  some 
flat  surface,  such  as  a  table,  upon  which  is  spread  a  sheet  of 


Fig.  39- 


white  paper,  and  focus  for  some  distant  scene,  more  than  1 50  or 
200  yards  off,  in  which  there  is  some  distinct  feature,  such  as  a 
church  spire  or  tall  chimney.  Make  the  image  of  this  fall  upon 
one  of  the  pencil  marks  on  the  focussing  screen,  and  with  a 
pencil  draw  a  line  upon  the  paper  along  the  side  of  the  camera ; 

198 


DICTIONARY  OF  PHOTOGRAPHY. 


[Foe 


now  bring  the  image  of  the  chimney  or  spire  upon  the  other  line, 
when  draw  another  line  upon  the  paper  also  along  the  side  of  the 
camera ;  remove  the  camera,  and  with  a  flat  rule  continue  these 
lines  till  they  cut  one  another,  so  as  to  form  an  angle,  across 
which  draw  a  line,  so  as  to  form  a  triangle,  which  line  must  be 
exactly  the  same  length  as  the  distance  between  the  two  pencil 
marks  on  the  focussing  screen.  Find  the  centre  of  this  base 
accurately,  and  connect  the  junction  or  apex  of  the  angular  lines 
with  the  centre  of  the  base.  This  line  will  then  be  the  true 
equivalent  focus  of  the  lens.  The  lines  aa'}  bb',  are  those  traced 
on  the  paper  along  the  sides  of  the  camera,  extended  until  they 
meet  at  c.  d  e  is  the  base,  being  the  exact  distance  apart  of  the 
two  pencil  marks  ;  /  its  centre,  and  cf  the  true  equivalent  focus 
of  the  lens. 

(2)  Method  by  Focussing  a  Given  Object  the  Same  Size.  With 
long-extension  cameras  a  very  common  method  is  to  focus  on 
any  object  till  the  image  is  exactly  the  same  size  as  the  object, 
then  measure  the  distance  between  the  object  and  ground-glass, 
and  divide  by  four,  when  the  result  will  be  the  equivalent  focus, 
A  convenient  object  to  use  is  a  foot  rule.  Example  : — On  focus- 
sing a  foot  rule,  till  the  image  or  part  of  it  measures  exactly  the 
same,  we  find  the  distance  between  object  and  ground-glass  to 
be  73£  in.  Then  73^-f4=i8f  in.,  the  focal  length  of  lens 
used. 

(3)  Schroeder  s  Method.  This  can  only  be  used  by  possessors 
of  a  telescope.  First  of  all  take  a  piece  of  cardboard — a  mount 
will  do — and  punch  two  holes  in  it  some  little  distance  apart  ; 


Fig.  40. 


place  this  card  flat  on  the  ground  side  of  the  focussing  screen, 
and  with  a  lead  pencil  blacken  the  ground-glass  through  the 
holes.  Now  go  into  a  darkened  room  and  set  up  the  card,  and 
place  behind  it  a  lamp  or  candle,  erect  the  camera,  and  rack  the 

199 


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DICTIONARY  OF  PHOTOGRAPHY. 


lens  in  or  out  till  the  bright  spots  of  light  coming  through  the 
holes  in  the  card  fall  exactly  on  the  black  spots  on  the  ground- 
glass,  and  mark  accurately  the  position  of  the  ground-glass  on 
the  base-board  of  the  camera,  as  shown  in  fig.  40,  in  which  a  is 
the  card  with  the  two  holes,  p  the  lens — here  represented  by  a 
single  double-convex  lens — and  b  the  focussing  screen,  marked 
by  the  pencil  with  the  two  black  dots,  on  which  are  focussed  the 
bright  spots  of  light  as  shown  by  the  dotted  lines.  A  small 
telescope  is  now  focussed  on  the  moon,  and,  the  focus  temporarily 


fixed,  the  ground-glass  is  removed  from  the  frame,  and  a  negative 
of  a  strong  contrasted  subject  is  placed  in  the  frame,  from  which 
the  ground-glass  has  just  been  removed.  A  very  good  negative, 
if  handy,  is  that  of  a  line-drawing.  The  eye-piece  of  the  tele- 
scope is  now  placed  in  the  same  position  as  the  card  previously 
used — i.e.,  opposite  the  lens  of  the  camera ;  a  candle  or  lamp  is 
placed  behind  the  negative,  and  the  camera  racked-in  till  the 


t 


Fig.  42. 

lines  of  the  negative  are  seen  sharp  and  clear.  Now,  as  the 
telescope  focus  has  been  fixed  for  infinity,  the  negative  will  only 
appear  sharp  when  it  is  at  the  true  focus  of  the  lens,  this  position 
is  then  accurately  marked,  as  shown  in  fig.  41,  in  which  t  is  the 
telescope  focussed  for  infinity,  p  the  lens,  and  d  h  the  position  of 
the  plane  of  the  negative.     Fig.  42  is,  as  will  be  at  once  seen,  a 

200 


DICTIONARY  OF  PHOTOGRAPHY. 


[Foe 


combination  of  the  two  previous  diagrams — figs.  40  and  41 — and 
the  distance  between  the  plane  1  and  plane  11  is  the  true  equivalent 
focus  of  the  lens  designated  in  the  diagram  by  F. 

(4)  Stolze's  Method.  This,  or  the  following  method,  No.  5, 
will  be  found  the  most  convenient  in  practice.  Dr.  Stolze 
described  his  method  in  "  Photographische  Nachrichten,  vol.  ii., 
p.  164,  1890,  as  follows  : — "One  first  focusses  on  a  very  distant 
object,  or,  so  to  speak,  on  infinity,  and  marks  this  position  of  the 
focussing  screen  on  the  base-board  of  the  camera.  Then  the 
camera  is  directed  at  a  very  near  upright  object  of  known,  or 
easily  measurable,  size — best  on  a  foot  rule — so  that  the  image 
falls  on  the  focussing  screen  ;  this  is  sharply  focussed,  and  this 
position  of  the  screen  again  marked  on  the  base-board  ;  a  negative 
is  taken  of  the  object  in  this  position,  and  after  development  the 
size  of  the  image  of  the  photographed  object  is  carefully  measured, 
and  one  thus  determines  how  much  smaller  the  former  is  than 
the  latter.  If  one  multiplies  the  difference  between  the  two  foci 
with  this  number,  the  result  will  be  the  focal  length."  Possibly 
an  example  will  make  this  a  little  clearer :  We  have  focussed 
on  a  very  distant  object,  and  marked  the  base-board,  and  have 
also  focussed  on  a  foot  rule  and  taken  a  negative,  and  find  that 
the  image  of  the  foot  rule  measures  10  in.,  the  distance  between 
the  two  marks  on  the  base-board  is  19  in.,  then 

F  =  19  x      =  22-8  in. 

The  size  of  the  image  should  be  as  large  as  possible — that  is  to 
say,  the  amount  of  reduction  should  be  as  little  as  possible, 
because  the  greater  the  reduction  the  less  accurate  the  result. 

(5)  Proportional  Method.  This  method  is  extremely  con- 
venient when  working  with  somewhat  short-focus  cameras  and 
long-focus  lenses.  The  camera  is  placed  upon  a  table,  when 
convenient,  or  if  such  is  not  handy,  on  the  ordinary  tripod.  We 
support  on  a  wall,  shelf,  or  convenient  place  a  foot  rule  which 
is  plainly  marked  in  inches.  On  the  ground-glass  of  the  camera, 
a  space  of  two  inches  is  accurately  marked  as  near  the  centre  as 
possible :  it  is  merely  necessary  to  mark  off  the  two  inches,  not 
to  divide  it  out  into  parts.  The  camera  is  now  moved  backwards 
or  forwards  till  the  image  of  the  foot  rule  of  twelve  inches  just 
falls  on  the  two-inch  space  we  have  marked  out.  The  coincidence 
of  the  image  on  the  lines  should  be  examined  with  an  eye-piece 

201 


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DICTIONARY  OF  PHOTOGRAPHY. 


or  compound  focusser,  to  see  that  they  do  coincide,  then  the 
distance  between  the  foot  rule  and  the  focussing  should  be  care- 
fully measured,  and  this  distance  jotted  down,  as  from  this  we 
obtain  the  focal  length  of  the  lens.  This  number  is  multiplied 
by  the  figure  which  represents  the  proportion  of  the  image  to 
the  original  object,  and  the  result  is  then  divided  by  the  square 
of  the  proportional  number  plus  one.  Taking  an  example,  we 
find  that  the  distance  between  the  foot  rule  and  its  image  equals 
63  ins. 

.\  63  x  6  =  378; 

378  -7-  49  =  7f  in.,  the  required  focal  length. 

It  must  not  be  thought  that  the  above  proportion  between  the 
object  and  its  image  is  essential ;  any  convenient  proportion 
may  be  taken,  such  as  4,  5,  8,  etc.,  but  the  rule  holds  good 
with  all. 

Parallel  rays  proceeding  from  any  object  and  transmitted 
by  a  convergent  lens  are  refracted  in  such  a  manner  that  they 
meet  at  a  point  and  form  an  image  of  that  object,  this  point 
being  called  the  principal  focus.  Rays  which  are  not  parallel  but 
which  diverge  from  an  object  are  transmitted  by  a  convex  lens  and 
united  to  a  point,  and  the  two  points  thus  connected  are  said  to 
be  conjugate  foci ;  or  in  other  words  the  distance  between  any 
point  in  any  object  and  the  lens,  and  the  distance  between  the 
lens  and  the  image  of  that  point,  are  said  to  be  the  conjugate  foci 
of  the  lens.  These  foci  are  of  great  importance  when  enlarge- 
ment or  reduction  of  any  print,  engraving,  or  negative  is  required. 
The  rules  for  finding  the  conjugate  focal  distances  are  given  under 
Enlargements  {q.v.),  and  a  table  of  same  in  the  Appendix  to  save 
any  calculation. 

Actinic  Focus.  As  has  been  stated  under  chromatic  aberration 
the  actinic  focus  is  not  actually  coincident  with  the  visual  focus, 
unless  the  lens  be  rendered  achromatic.  (See  also  Testing 
Lenses.) 

Depth  of  Focus  is  the  power  of  defining  upon  a  plane  surface, 
with  sufficient  definition  to  satisfy  the  requirements  of  artistic 
ideas,  the  images  of  objects  situated  at  varying  distances. 
Theoretically  this  is  an  impossibility,  but  practicality  when  any 
point  is  focussed  sharply  there  is  a  certain  distance  before  and 
behind  that  point  which  is  also  sharp.    To  find  this  distance  the 

202 


DICTIONARY  OF  PHOTOGRAPHY. 


[Foe 


following  rule  may  be  used.  The  use  of  diaphragms  increases  it ; 
the  smaller  the  aperture  the  greater  the  depth  of  focus.  Having 
focussed  any  point,  to  find  the  distance  in  front  of  that  point 
which  will  be  in  focus  (all  measurements  to  be  in  inches,  and  the 
distance  of  object  to  be  measured  from  the  optical  centre  of 
lens) — (i)  Multiply  the  focal  length  by  the  diameter  of  the  stop, 
and  the  result  by  the  difference  between  the  focal  length  and 
the  distance  of  the  object.  (2)  Multiply  the  focal  length  by  the 
diameter  of  the  stop,  and  add  T£7  part  of  the  distance  of  the 
object.  (3)  Divide  the  first  product  by  the  last,  add  the  focal 
length,  and  subtract  the  result  from  the  distance  of  the  object, 
when  the  result  will  be  the  distance  sought  for  in  front  in  inches. 
To  find  the  depth  of  focus  behind  a  given  point— (1)  Multiply 
the  focal  length  by  the  diameter  of  the  stop,  and  the  result  by  the 
difference  between  the  focal  length  and  the  distance  of  the 
object.  (2)  Multiply  the  focal  length  by  the  diameter  of  the  stop, 
and  subtract  rJ5  part  of  the  distance  of  the  object.  (3)  Divide 
the  first  product  by  the  last,  add  the  focal  length,  and  deduct  the 
distance  of  the  object ;  the  result  is  the  distance  behind  in  inches. 

Example : — Find  the  depth  of  focus  when  focussing  an  object 
15  ft.  distant  with  a  lens  of  7-in.  focus,  working  at //5- 

//5  =  If  in.       15  ft.  =  180  in. 
7  x  [{  = 
180  -  7  =  173. 
49  X  H77 

5  5 

7  x  !!  =  -¥• 
49    180^42  9^58 
5     100     5     5  s 

8477  .  58     8477  . 

^-5  =  58  =I46' 

146  +  7  =  153       180  -  153  =  27  in.  (3). 

The  depth  of  focus  in  front  =  27  in. 

Example : — To  find  the  depth  behind. 

7x1$  =  -^       1 80  -  7  =  1 73. 

203 


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DICTIONARY  OF  PHOTOGRAPHY. 


7  x  i  =  -V-. 

49  _  i8o  =  49  _  9  =  4o 
5      100      5      5  5 

8477^  40  =  8477  =  2IQ 

5     '   5  4o 
210  +  7  =  217      217-180  =  37. 

The  depth  of  focus  behind  =  37  in. 
Focussing  Glass,  or  Compound  Focusser.  A  small  telescopic 

magnifying  eye-piece,  used  to  obtain  microscopic  sharpness  of 
focus  upon  the  ground-glass,  and  it  should  be  invariably  used  by 
every  amateur,  especially  those  who  desire  to  enlarge  the  result- 
ing negatives. 

Focussing  Screen.  The  ground-glass  upon  which  the  image 
formed  by  the  lens  is  seen.  The  best  glass  to  use  for  this 
purpose  is  patent  obscured  plate,  obtained  by  grinding  patent 
plate  with  very  fine  emery.  To  make  a  screen  of  ground-glass 
coarse  emery  powder  should  be  made  into  a  paste  with  water, 
and  lightly  rubbed  over  a  piece  of  glass,  using  a  small  painters' 
muller,  or  any  other  convenient  flat  surface  for  grinding,  till  the 
surface  begins  to  show  signs  of  abrasion,  when  the  coarse  emery 
should  be  completely  washed  off,  and  the  finest  emery  obtainable 
used  till  the  glass  is  obscured  enough.  Two  pieces  of  glass  can 
be  ground  at  the  same  time  by  fixing  a  small  cork,  or  anything 
that  will  serve  as  a  handle,  on  to  one  piece  of  glass,  with  a  piece 
of  cobbler's  wax  or  pitch,  and  using  the  one  to  grind  the  other. 
Should  the  focussing  screen  be  accidentally  broken,  a  piece  of 
plain  glass  daubed  over  with  putty,  or  coated  with  a  paste  of 
flour  and  water,  or  at  a  pinch  a  fine  cambric  handkerchief,  may 
be  used.  The  following  solution  spread  on  glass  has  been  sug- 
gested as  a  substitute  for  the  ground-glass  : — 

White  wax   120  grs.  or  7  grms. 

Ether   1  ozs.  „   28  c.cm. 

Or  the  following  matt  varnish  : — 

Sandarac      ...       ...       ...      18  grs.  or  1  grm. 

Mastic    4  „     „  -3  „ 

Ether  200  mins.  „  12  c.cm. 

Benzole    80  to  100    „  5  to  6  c.cm. 

204 


DICTIONARY  OF  PHOTOGRAPHY.  [Fog 

The  more  benzole  the  finer  the  matt  surface  obtained.  Or  an 
ordinary  negative  varnish,  containing  one  per.  cent,  of  tartaric 
acid ;  or  a  very  good  substitute  may  be  obtained  by  soaking 

Gelatine  or  glue    60  grs.    or    4  grms. 

In  water    4  drms.  ,,    14  c.cm. 

and  adding 

Boiled  milk  ...       ...       ...       2  drms.  or  7  c.cm. 

melting  by  the  aid  of  a  gentle  heat,  and  flowing  over  the 
glass. 

Aids  to  Focnssi?ig.  Oiling  the  screen  renders  the  grain  of  the 
glass  but  very  little  perceptible.  Or  a  better  expedient  still  for 
use  with  the  compound  focusser  is  a  microscopic  covering  glass 
cemented  to  the  ground  surface  of  the  screen  with  a  drop  of 
Canada  balsam  ;  a  small  cross  should  be  marked  in  lead  pencil 
on  the  ground  surface  before  doing  this  or  else,  through  the  ready 
accommodation  of  the  focus  of  the  eye,  this  plan  will  prove  a 
hindrance  rather  than  a  help.  Both  the  cross  and  image  should 
be  in  focus  together. 

Fog  is  one  of  the  commonest  of  all  faults  with  gelatine  nega- 
tives, and  is  seen  as  a  veil  over  the  whole  negative,  and  is  a 
deposit  of  silver  upon  the  shadows  more  or  less  dense  according 
to  the  greatness  or  slightness  of  the  fog.  There  are  two  great 
divisions  of  fog — chemical  and  light  fog.  The  former  is  caused 
by  errors  in  the  manipulation  of  the  plate  manufacture,  or 
in  development ;  the  second  by  the  impact  of  light,  as  through 
some  crevice  in  the  camera  or  dark  slide,  or  through  over- 
exposure. 

Chemical  Fog,  from  errors  in  manufacture,  may  be  traced  to 
several  causes,  the  chief  being  an  abnormal  excess  of  silver 
nitrate  in  the  emulsion,  and  also  by  decomposed  gelatine,  caused 
by  too  long  stewing,  when  the  emulsion  is  made  by  the  boiling 
process.  If  the  fog  is  very  bad,  there  is  no  cure  for  it,  but  when 
slight  the  emulsion  may  be  squeezed  through  coarse  canvas  or 
muslin,  as  described  under  Emulsions  (c/.v.),  into  a  solution  of 
bichromate  of  potash,  ten  grains  to  the  ounce,  and  allowing  it  to 
stand  for  one  hour,  then  washing  for  two  hours  in  running  water, 
or  the  addition  of  a  few  grains  of  cupric  chloride  or  auric  chloride 

205 


For] 


DICTIONARY  OF  PHOTOGRAPHY. 


will  generally  effect  a  cure.  Chemical  fog  is  often  seen  as 
iridescent  green  stains  near  the  edges  of  plates,  and  is  likely 
to  make  its  appearance  with  an  ammonia  developer ;  it  is  less 
likely  to  ensue  with  the  fixed  alkalies,  potash  and  soda,  and 
rarely  with  ferrous  oxalate.  The  obvious  remedy  for  this  evil, 
with  a  brand  of  plate  known  to  be  liable  to  green  fog,  is  the  use 
of  potash  and  soda  or  ferrous  oxalate  ;  but  where  it  does  exist  it 
can  be  eliminated  by  treating  the  plate  after  fixing  and  washing 
with 

Ferric  chloride       ...       ...      50  grs.  or  3.2  grms. 

Potassium  bromide  ...       ...      30  ,,    ,,  1*9  grm. 

Distilled  water    4  ozs.  „  118  c.cm. 

Soak  the  plate  in  this  for  a  minute  or  two,  when  it  will  be  found 
that  the  fog  will  disappear,  and  the  plate  be  reduced  in  density  ; 
rinse  well,  and  then  apply  a  ferrous-oxalate  developer,  when 
the  required  density  can  be  obtained  ;  the  plate  should  be  then 
refixed  and  washed. 

Light  Fog  makes  its  appearance  generally  all  over  the  plate, 
and,  as  has  been  stated  above,  may  be  due  to  three  causes. 
When  the  fault  is  supposed  to  lie  in  the  camera  (and  the  reason 
to  suspect  this  is  to  find  the  edges  of  plate  covered  by  rabbet  of 
slide  free  from  fog),  cap  the  lens,  remove  the  focussing  screen, 
cover  the  head  with  the  focussing  cloth,  and  carefully  examine 
the  interior  of  camera  to  see  if  any  stray  thread  of  light  is 
admitted.  The  plate  may  be  fogged  in  the  dark  slide,  and  the 
effect  will  be  seen  on  development  by  certain  streaks  and  bands 
of  fog  making  their  appearance,  a  very  usual  place  being  at 
the  leather  hinge  which  allows  the  shutter  of  this  slide  to  be 
folded  back,  and  this  fog  seems  to  be  not  only  due  to  light,  but 
in  many  cases  is  actually  induced  by  the  material  or  something 
used  in  making  the  hinge.  It  may  also  make  its  appearance  at 
the  side  where  the  manufacturer  places  the  small  slips  of  card- 
board to  separate  the  plates,  and  in  this  case  it  is  due  to  some 
impurity  in  the  paper  used.  Stray  actinic  light  or  an  imperfect 
non-actinic  light  in  the  dark-room  may  also  cause  general  fog, 
and  if  this  be  suspected  the  light  should  be  tested  as  described 
under  Dark-Room. 


Formic  Acid.    (Ger.,  Ameisensaure  ;  Fr.,  Acide  Formique). 
206 


DICTIONARY  OF  PHOTOGRAPHY. 


[Fri 


HCH02=46.  An  acid  liquid  prepared  by  oxidation  from  starch, 
but  was  originally  obtained  from  ants,  whence  its  name.  This 
has  been  recommended  as  preservative  of  pyro,  and  the  writer 
has  found  that  half  an  ounce  of  dilute  formic  acid  will  preserve 
i  oz.  of  pyrogallol  even  when  exposed  to  light  and  air  for  over 
two  months,  but  when  mixed  with  the  accelerator  the  developer 
turns  thick  and  muddy  quicker  than  plain  pyro. 

Frilling.  By  this  is  meant  the  gelatine  leaving  the  plates  in 
folds  or  wrinkles.  It  usually  begins  at  the  edges,  and  occurs 
chiefly  when  fixing,  but  often  during  development  or  washing. 
The  causes  are  numerous,  but  as  most  of  these  are  but  slightly 
under  the  control  of  the  operator  they  will  only  be  enumerated, 
and  the  possible  cures  given  at  length.  The  chief  cause  is  the 
use  of  a  gelatine  of  ;too  horny  a  nature,  and  possessing  but  little 
tenacity.  Again,  long-continued  boiling  of  an  emulsion  especially 
tends  to  this  evil ;  an  improperly  washed  plate,  unequal  drying, 
and  excessive  slowness  of  the  emulsion  in  setting,  due  to  the  use 
of  a  soft  gelatine  or  the  heat  of  the  weather,  or  by  allowing  too 
forcible  a  stream  of  water  to  impinge  upon  the  edge  of  a  plate, 
or  the  use  of  an  exceeding  strong  developer,  or  the  differing 
temperatures  and  densities  between  the  developing,  fixing,  and 
washing  fluids.  The  remedy  for  some  causes  are  obvious  ;  but 
with  the  ordinary  run  of  amateurs,  who  are  not  plate-makers, 
when  a  batch  of  plates  purchased  is  found  to  be  subject  to 
frilling,  they  should,  if  possible,  be  kept  for  two  or  three  months, 
when  the  fault  will  be  nearly,  if  not  completely,  eradicated  ;  but 
where  this  remedy  is  impracticable,  or,  by  reason  of  the  number 
of  the  plates  being  but  small  is  hardly  desirable,  the  following 
immediate  steps  may  be  taken.  The  plate,  before  development, 
may  be  coated  with  collodion  made  as  follows  : — 

Pyroxyline    ...       ...       ...    6  grs.     or     -4  grms. 

Alcohol  (-820)    A  oz.      ,,   12-5  c.cm. 

Ether  (735)  i  »       »  ^  S  „ 

Castor  oil     ...    4  drops  ,,       3  ,, 

When  this  is  used,  the  plate,  after  being  collodionised,  must 
be  well  washed  with  clean  water  till  it  no  longer  repels  water 
from  the  surface  of  the  film.  When  the  plate  is  collodionised,  it 
is  advisable  to  add  about  10  per  cent,  of  methylated  alcohol  to 

207 


Gal] 


DICTIONARY  OF  PHOTOGRAPHY. 


developer.  Soaking  the  plates  in  the  following  for  five  minutes 
is  an  absolute  cure,  but  it  prolongs  development : — 

Chrome  alum    2  grs.  or  -2  grm. 

Dissolved  in 

Water  ...    ...    1  oz.  or  25  c.cm. 

Add 

Methylated  spirit    1  oz.  or  25  c.cm. 

But  the  author  has  found  the  following  an  unfailing  remedy,  and 
by  its  use  development  is  not  so  much  prolonged  : — Have  by 
the  side  of  the  developing  or  fixing  bath  a  dish  of  methylated 
spirit,  and  if  the  slightest  sign  of  frilling  or  blisters,  which  are 
but  localised  frilling,  makes  its  appearance,  immerse  the  plate 
immediately  in  the  spirit  till  the  frill  disappears,  then  proceed 
with  development  or  fixing.  Some  plates  frill  at  the  edges  only  ; 
for  these  an  edging  of  grease  or  india-rubber  solution  is  the 
remedy.  When  plates  are  found  to  frill  in  the  fixing,  but  not  in 
developing,  an  intermediate  soak  in  the  chrome  alum  Clearing 
Bath  (q.v.)  will  prevent  it. 

Fuming.  The  process  of  subjecting  silver  albumenised  paper 
to  the  vapour  of  ammonia.  It  is  claimed  for  this  that  it  renders 
the  prints  more  brilliant,  that  the  paper  prints  quicker,  and 
that  it  makes  the  tones  of  the  finished  print  purple,  without 
much  trouble.  Many  elaborate  boxes  have  been  designed  for 
this  purpose,  but  the  simplest  and  a  really  efficient  plan  is  to 
use  an  old  cardboard  plate  box,  and,  having  cut  the  paper  to  the 
required  size,  pin  it  by  the  four  corners  face  downwards  to  the 
lid,  and  on  the  bottom  inside  sprinkle  a  few  drops — about  ten  or 
fifteen — of  liquor  ammonia  -88o,  put  on  the  lid,  anpl  leave  it  for 
ten  minutes  in  hot  and  fifteen  in  cold  weather.  Paper  when  once 
fumed  should  be  used  within  two  or  three  days,  or  the  good 
effect  will  be  lost.  Fumed  paper  is  more  liable  to  discolour  than 
ordinary.  The  after-operations  of  washing,  toning,  and  fixing  are 
precisely  the  same  as  usual. 

Gallic  Acid  (Ger.,  Gallussaure ;  Fr.,  Acide  gallique ;  Ital., 
Acido  gallico).  HC7H505  ==  170.  Obtained  by  fermentation 
from  powdered  galls.    Solubility  1  per  cent,  in  cold,  33  per  cent. 

.  208 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gel 


in  boiling  water,  very  soluble  in  alcohol,  less  so  in  ether.  It  was 
used  fordevelopingin  the  collodion  and  waxed  paper  processes,  and 
has  been  also  suggested  for  developing  gelatino-chloride  paper. 

Gallon.    See  Weights  and  Measures. 

Gamboge,  or  Camboge  (Ger.  Gummigutti ;  Fr.  Gomme  Gutte  ; 
Ital.  Gomma  Gutta).  An  orange-coloured  gum  resin,  from  the 
Garcinia  Morella,  a  native  of  Siam  and  Cochin  China.  The 
finest  is  that  called  "  Pipe  Gamboge,"  which  is  collected  in 
bamboo  canes.  The  inferior  is  called  cake  gamboge.  It  is 
almost  entirely  soluble  in  alcohol,  and  when  rubbed  down  with 
water  forms  a  thick  emulsion  of  a  brilliant  yellow  colour.  It 
has  but  little  taste,  and  no  smell.  It  is  used  but  rarely  in 
photography,  being  sometimes  the  colouring  matter  of  varnishes 
and  lacquers.  The  action  upon  human  beings  when  taken 
internally  is  that  of  a  most  drastic  and  hydragogue  cathartic. 

Gelatine.    An  animal  substance  obtained  by  boiling  bones, 
hoofs,  horns,  and  other  animal  substances.    It  contains  about 
15  to  20  per  cent,  of  water  at  ordinary  temperatures,  and  in  cold 
water  swells  up  and  absorbs  from  five  to  ten  times  its  weight. 
Good  samples  will  absorb  sufficient  water  to  dissolve  them  when 
the  temperature  is  raised  above  900  F.,  the  solution  setting 
again  to  a  jelly  on  cooling.    The  continued  application  of  heat  for 
some  time  destroys  this  setting  powder,  a  new  compound  called 
metagelatine   being   formed.    Gelatine   will   keep  indefinitely 
in  the  dry  state,  but  in  the  presence  of  water  it  soon  putrefies, 
turning  first  acid,  and  then  alkaline,  and  at  this  stage  ammoniacal 
vapours  are  given  off.     Alum,  alcohol,  carbolic,  salicylic,  and 
boracic  acids,  thymol,  and  the  salts  of  zinc  act  as  antiseptics. 
Acetic,  hydrochloric,  sulphuric,  and  oxalic  acids  dissolve  gelatine 
even  in  the  cold — acetic  acid  the  most  readily.    Carbolic  acid 
and  alcohol  precipitate  it  from  aqueous  solutions  when  they 
are  in  excess.    Silver  nitrate  exposed  to  sunlight  in  contact  with 
gelatine  produces  a  red  colour,  due  to  a  compound  of  gelatine 
and  suboxide  of  silver.    The  alkaline  dichromates  in  solution  of 
gelatine  render  the  latter  after  exposure  to  light  insoluble  and 
incapable  of  absorbing  water,  this  action  being  the  basis  of  the 
carbon   and   nearly  every  photo-mechanical  printing  process. 
Chrome  alum  and  tannin  render  it  insoluble,  but  capable  of 
absorbing  water.    Ordinary  alum  raises  the  melting  point,  but 

209  p 


Gel] 


DICTIONARY  OF  PHOTOGRAPHY. 


does  not  render  it  insoluble.  The  composition  of  gelatine  varies 
with  the  source  from  which  it  is  obtained,  but  the  following  may 
be  taken  as  the  percentage  composition  : — 

Carbon    50*1 

Hydrogen  ...       ...       ...       ...       ...  6-6 

Nitrogen    18-3 

Oxygen    25-0 

Sulphur    o-i2 

The  selection  of  a  gelatine  suitable  for  emulsion  making  is  a 
most  important  point,  but  the  following  leading  characteristics 
of  a  suitable  kind  may  be  of  service  to  the  amateur  plate  manu- 
facturer : — The  weight  of  the  ash  left  after  incineration  should 
never  exceed  2  per  cent.,  proving  the  absence  of  earthy  or 
mineral  matter.  The  amount  of  water  it  will  absorb  should  in 
no  case  exceed  ten  times  nor  be  less  than  five  times  its  weight. 
For  emulsion  making  by  the  boiling  process  it  should  give  an 
acid  reaction,  and  its  solubility  should  not  be  affected  at  a  lower 
temperature  than  70°  F.,  nor  higher  than  no°  F.  Another 
most  important  test  is  its  expansive  power,  for  upon  this  depends 
to  a  great  extent  its  frilling  or  non-frilling  properties.  The 
following  table  of  the  chief  characteristics  of  the  best  com- 
mercial brands  will  be  of  practical  use  ;  but  it  may  be  stated  that 
the  best  film  can,  as  a  rule,  be  obtained  by  a  mixture  of  one  part 
of  hard  and  two  parts  of  soft  gelatine  : — 


Water 

Ash. 

Absorbed. 

Name. 

Charac- 

Per 

Times  in 

ter. 

Cent. 

Weight. 

Coignet's  gold  label 

hard 

I 

..  n 

2. 

,,  special... 

>) 

I 

3- 

Nelson's  No.  1  pho- 

tographic   

soft 

2 

..  6 

4- 

Nelson's  opaque  ... 

hard 

2 

5- 

,,       amber  ... 

soft 

I 

...  4f 

6. 

Swinborne   No.  2 

isinglass   

>»  • 

..    '  I 

..  6i 

7. 

Russian  isinglass 

a 

8. 

Simeon's  Swiss  ... 

hard 

I 

..  8| 

9- 

Heinrich's   

...  I 

...  8| 

Nos.  1,  3,  8,  and  9  are  the  best  to  use, 
210 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gel 


It  is  always  better  to  make  a  small  batch  of  emulsion  first,  with 
a  sample  of  gelatine,  to  test  its  suitability,  rather  than  have  a 
large  batch  spoilt  by  finding  the  gelatine  used  totally  unsuitable. 
Gelatine  has  a  great  affinity  for  bromine,  chlorine,  and  iodine, 
and  upon  this  fact  depends  to  a  great  extent  their  increased 
sensitiveness  over  collodion  plates. 

Gelatino-Chloride  Emulsion  Paper.  This  is  an  outcome  of 
collodio-chloride  emulsion  paper,  which  was  known  in  England 
as  Simpson-type  ;  just  as  gelatine  took  the  place  of  collodion  for 
plates,  so  gelatine  replaced  the  collodion  for  this  purpose,  J.  B. 
Obernetter,  of  Munich,  being  the  first,  we  believe,  to  make  the 
gelatino-chloride  emulsion  paper.  The  following  formulae  will 
be  found  all  that  can  be  desired  for  making  the  same  : — 

No.  I. 

Gelatine       ...       ...       ...    230  grs.     or  15  grms. 

Distilled  water       ...       ...       6  drms.  ,,    22  c.cm. 

Soak  for  an  hour  and  dissolve  by  the  aid  of  a  gentle  heat,  and 
add 

Nitrate  of  silver    6  grs.  or  4  grms. 

To  this  mixture  add  gradually 

Lithium  chloride     ...       ...       1  gr.      or  *o6  grm. 

Tartaric  acid ...    1  ,,       „    06  „ 

Distilled  water    1  drm.  ,,     3  c.cm. 


No.  II. 

Nelson's  soft  gelatine 
Heinrich's  hard  gelatine  ... 
Ammonium  chloride 
Distilled  water   


139  grs.     or      9  grms. 

293    -       m  19  h 

54o  tt       „  35  » 

100  drms.  ,,  360  c.cm. 


Allow  to  soak  for  half  an  hour,  and  dissolve  by  the  aid  of  a 
water  bath,  and  add  gradually,  almost  drop  by  drop,  with  constant 
stirring,  the  following  at  about  900  F.  : — 


Nitrate  of  silver    154  grs.     or  10  grms. 

Distilled  water    336  mins.   ,,  20  c.cm. 


Gel] 


DICTIONARY  OF  PHOTOGRAPHY. 


Allow  the  emulsion  to  set  hard,  press  through  canvas,  wash  in 
four  changes  of  water  five  minutes  each,  and  drain  well.  Now 
prepare  the  following  : — 


Soak  for  half  an  hour  and  dissolve,  and  add  the  following  at  a 
temperature  of  900  F.,  with  constant  stirring  : — 

Sodium  citrate  (neutral)  ...  30  grs.  or  2  grms. 
Distilled  water       ...       ...    170  mins.  ,,  10  c.cm. 

Dissolve 

Nitrate  of  silver      ...       ...      46  grs.  or   3  grms. 

Citric  acid    77   „  „     5  „ 

Distilled  water       ...       ...  170  mins.  ,,    10  c.cm. 

Add  to  the  citrate  and  gelatine  very  gradually,  constantly  stirring, 
set  quickly  and  wash  in  five  changes  of  water  five  minutes 
each,  drain  well,  and  add  to  the  chloride  emulsion  as  above, 
and  add 

Citric  acid    ...       ...       ...      15  grs.     or  1  grm. 

Distilled  water    119  mins.  ,,  7  c.cm. 

Allow  the  emulsion  to  stand  in  a  fluid  state  for  one  hour, 
occasionally  stirring.  Keep  for  three  days,  and  then  coat  the 
paper. 


Mr.  W.  K.  Burton  gives  the  following.  Two  separate  emulsions 
are  made  as  in  the  last  case : — 


Heinrich's  gelatine  ... 
Distilled  water 


100  grs.  or  6*5  grms. 
150  mins.  ,,     9  c.cm. 


No  III. 


A. 


Ammonium  chloride 
Gelatine 
Distilled  water 


53  grs.  or  3-5  grms. 
420  „    „    63  „ 
30  ozs.  ,,  500  c.cm. 


212 


DICTIONARY  OF  PHOTOGRAPHY.  [Gel 

Allow  to  soak  for  an  hour,  and  dissolve  by  the  aid  of  a  water 
bath  ;  then  add 


Nitrate  of  silver      ...       ...    150  grs.  or  10  grms. 

Distilled  water       ...       ...        ^  oz.        12  c.cm. 


B. 

.Sodium  citrate    30  grs.  or    2  grms. 

Gelatine      ...       ...       ...  100  6*5 

Distilled  water       ...       ...  3^  ozs.  „  100  c.cm. 


Soak  for  an  hour,  dissolve  by  heat,  and  add 

Nitrate  of  silver    45   grs.  or  3  grms. 

Citric  acid   80     ,,    ,,     5  ,, 

Distilled  water       ...       ...        ^  oz.   „  14  c.cm. 

Mix  both  emulsions.  Allow  to  set,  and  wash  as  directed  for 
No.  II.  emulsion.  The  same  authority  also  suggests  the  following 
formulae  and  method  of  mixing  the  same  : — 

Formula  No.  1. 
A.  Nitrate  of  silver     ...       ...       ...       ...    400  grs. 

Water    4  ozs. 


B.  Gelatine,  soft         ...    ...  80  grs. 

Chloride  of  ammonium  ...       ...  ...  80  ,, 

Citric  acid    ...       ...  ...  120  ,, 

Water    ...       ...  ...       8  ozs. 


Formula  No.  2. 

A.  Nitrate  of  silver   400  grs. 

Water    4  ozs. 


B.  Gelatine  (soft)        ...  ...       ...       ...      80  grs. 

Chloride  of  ammonium  ...       ...       ...      80  ,, 

Citric  acid    ...       ...       ...  120  ,, 

Carbonate  of  soda  (dry)    45  ,, 

Water    ...       8  ozs. 


Gel] 


DICTIONARY  OF  PHOTOGRAPHY. 


Formula  No.  3. 

A.  Nitrate  of  silver      ...       ...       ...       ...    400  grs. 

Water  ...    ...       ...       4  ozs. 

B.  Gelatine  (soft)    80  grs. 

Chloride  of  ammonium    80  „ 

Citric  acid    ...       ...       ...       ...       ...  60  ,, 

Carbonate  of  soda  (dry)    ...       ...       ...  80  ,, 

Water    8  ozs. 

The  first  formula  gives  an  emulsion  suitable  for  preparing  paper 
to  be  used  for  printing  from  dense  negatives,  the  second  from 
medium  negatives,  and  the  third  from  thin  negatives.  The  third 
formula  is,  I  am  afraid,  dreadfully  unorthodox,  for  Mr.  Burton 
says  :  "  There  is  just  about  enough  of  ammonium  chloride  and  of 
sodium  citrate  formed  by  the  double  decomposition  of  the  citric 
acid,  and  of  part  of  the  soda  to  decompose  the  whole  of  the 
nitrate  of  silver.  The  formula  works  all  right,  and  the  paper  that 
results  from  the  use  of  it  keeps  very  fairly.  The  paper  resulting 
from  either  of  the  other  formula  will  probably  keep  as  long  as 
any  sensitised  paper.  The  following  is  the  method  of  emulsify- 
ing. The  two  solutions  are  heated  to  a  temperature  of  1  io°  to 
1200  F.  The  temperature  should  not  be  greater  than  1200,  or 
there  is  a  great  chance  that  some  of  the  insoluble  silver  salts 
produced  will  be  thrown  down  in  the  granular  orm.  A  is  then 
added  slowly  to  B  with  much  stirring.  The  emulsion  is  filtered 
through  a  double  thickness  of  cambric,  and  is  then  immediately 
ready  for  use.  If  it  is  wished  to  keep  the  emulsion  for  any 
length  of  time,  10  per  cent,  of  alcohol,  in  each  ounce  of  which  a 
few  grains  of  thymol  have  been  dissolved,  should  be  added  to  the 
emulsion.  It  is  to  be  observed,  however,  that,  even  with  this 
addition,  emulsion  by  formula  No.  3  will  not  keep  for  very  long.'' 
Mr.  Burton  recommends  floating  the  paper  for  three  or  four 
minutes  to  coat  it,  or  by  brushing  the  emulsion  over  the  paper, 
allowing  it  to  get  surface  dry  and  repeating  the  operation.  The 
temperature  of  coating  room  should  be  700  F.  The  above  quantity 
of  emulsion  will  coat  eight  sheets  22  by  17,  or  ten  or  twelve 
by  floating.  Either  gold  or  platinum  may  be  used  for  toning,  but 
the  prints  should  be  well  washed  first.  The  best  method  of 
coating  the  paper  is  a  question  of  quantity  :  in  small  quantity  the 

214 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gel 


paper  should  be  wetted  thoroughly  in  warm  water,  and  squeegeed 
to  a  sheet  of  glass,  and  the  emulsion  poured  on  it ;  with  larger 
quantities  the  sheets  should  be  drawn  over  the  surface  of  the 
fluid  emulsion.  The  majority  of  operators  will  no  doubt  prefer 
to  buy  their  paper  ready  made,  and  the  following  may  be 
considered  as  the  necessary  manipulations  for  producing  perfect 
prints,  although  this  paper  undoubtedly  gives  its  best  results 
when  used'for  rather  thin  negatives  or  those  wanting  in  contrasts. 
The  paper,  cut  to  the  required  size,  is  placed  in  contact  with  the 
film  side  of  the  negative  in  the  ordinary  printing  frame,  and 
placed  in  a  good  printing  light.  Where  the  negative  is  exception- 
ally thin  the  frame  should  be  placed  in  a  weak  light  with  opal  or 
green  glass  over  it,  where  the  contrasts  are  greater  use  a  stronger 
light ;  examine  the  print  during  the  operation  of  printing  in  a 
very  subdued  light,  and  great  care  must  be  exercised  that  the 
paper  does  not  shift  whilst  thus  examining  it,  as  it  is  very  likely 
to  do  from  its  highly  polished  surface.  As  a  preventative  a  pad 
of  felt,  or  two  or  three  thicknesses  of  stout  blotting  paper  should 
be  used.  On  the  depth  of  printing  depends  to  a  great  extent  the 
tone  of  the  resulting  print ;  it  is  our  practice  when  using  this 
paper  to  carry  the  printing  sufficiently  far,  so  as  to  give  the  very 
highest  lights  a  decided  tinge,  and,  if  black  tones  are  required, 
till  the  highest  lights  are  deeply  coloured.  After  printing,  the 
pictures  should  be  carefully  preserved  from  damp  and  light,  and 
thus  may  be,  if  necessary,  kept  till  some  considerable  number 
are  collected,  as  they  deteriorate  but  little  by  being  kept  a  week 
or  even  longer.  For  toning,  numerous  baths  have  been  suggested 
to  give  various  tones  ;  most  operators  get  into  a  particular  groove 
of  working  special  photographic  papers,  and  from  some  consider- 
able experience  I  can  recommend  the  following  method  of  pro- 
cedure as  conducive  to  good  results.  The  first  consideration  is 
the  negative ;  every  negative  is  not  suitable  for  this  paper, 
though  every  negative  will  give  a  print  on  it.  Those  negatives 
which  have  very  weak  shadows  and  dense  high  lights  give 
unsatisfactory  results  because  there  is  a  tendency  in  the  paper  to 
give  an  increased  contrast,  and  for  this  very  reason  it  is  excep- 
tionally valuable  for  weak  or  somewhat  thin  negatives.  For 
veritable  ghosts,  then,  we  can  use  green  or  yellow  glass  in  front 
of  the  negative,  or  tissue  paper  or  opal,  so  as  to  reduce  the  light, 
and  print  in  weak  diffused  light.    For  stronger" negatives  we  can, 

215 


Gel]  DICTIONARY  OF  PHOTOGRAPHY. 

of  course,  print  in  stronger  light.  The  question  how  far  to  carry 
printing  is  an  important  one  and  a  good  deal  depends  upon  the 
toning  bath  that  is  used.  Practically  it  may  be  said  that  the 
paper  should  be  exposed  till  there  is  a  decided  tinge  on  the  high 
lights.  Chloride  paper  may  be  kept  some  weeks  before  toning  if 
actually  required,  but  it  is  not  advisable  to  keep  it  too  long,  or  the 
whites  suffer  and  it  is  more  difficult  to  tone.  We  must  now  enter 
slightly  into  the  chemical  composition  of  gelatino-chloride  emul- 
sions. All  commercial  papers,  we  believe,  contain  chloride  of 
silver,  with  some  organic  salt,  usually  citrate  of  silver,  with  free 
nitrate  of  silver,  and  frequently  citric  acid.  The  nitrate  and 
citrate  are  soluble  in  water,  and  cause  the  milkiness  which  is 
apparent  when  chloride  prints  are  placed  in  water.  These  should 
be  got  rid  of  before  toning  or  else  they  contaminate  the  toning 
bath,  and  in  the  case  of  the  alkaline  baths,  such  as  the  acetate  or 
borax,  the  prints  must  be  free  from  any  acid,  or  else  the  bath 
becomes  acid,  and  tones  but  slowly  or  not  at  all.  If  the  sulpho- 
cyanide  bath  be  used,  free  silver  salts  mean  the  formation  of 
silver  sulphocyanide,  the  bath  will  not  keep,  and  toning  is 
rendered  more  difficult.  In  the  case  of  the  combined  bath  we 
have  hypo ;  and  to  place  a  print  containing  acid  in  this  means 
decomposition  of  the  hypo  and  sulphurisation  and  degradation  of 
the  whites.  As  soon  as  sufficient  prints  are  obtained,  for  it  is  not 
worth  while  toning  one  or  two,  make  a  solution  of  salt,  ordinary 
household  salt,  2  oz.  to  the  pint  of  warm  water.  When  dissolved 
and  cool,  place  the  prints  in  the  solution  and  keep  them  on  the 
move  for  ten  minutes,  pour  away  the  salt,  and  wash  for  ten 
minutes  in  plain  water.  The  use  of  salt  renders  toning  some- 
what slower,  more  even,  and  obviates  any  free  soluble  silver  salt. 
If  the  prints  are  washed  in  water  first,  the  salt  being  omitted,  it 
is  necessary  to  change  the  waters  very  quickly,  or  yellowed 
whites  will  be  the  result,  from  the  silver  combining  with  the 
paper  and  gelatine.  It  is  preferable  to  use  salt  or  carbonate  of 
soda,  the  latter  in  the  proportion  of  1  oz.  to  the  pint — I  prefer 
the  salt.  Now  with  regard  to  the  toning  bath.  When  matt- 
surface  papers  were  introduced,  I  started  a  series  of  experiments, 
using  one  print  of  matt  and  one  of  glossy  paper,  and  tried  the 
usual  baths,  acetate,  borax,  phosphate,  carbonate,  and  sulpho- 
cyanide, and  found  that  with  all  but  the  last  there  was  a  tendency 
to  pinky  tones,  and  this  was  puzzling  for  some  time,  till  the  con- 

216 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gel 


elusion  was  come  to  that  it  was  due  to  the  action  of  the  gold  upon 
very  faint — too  faint  to  be  visible — impression  of  light  upon  the 
silver  salt.    This  was  confirmed  by  the  curious  pinkish  tinge  on 
vignettes.    An  instructive  experiment  was  then  made  :  a  letter 
was  cut  out  of  deep  ruby  paper  and  placed  in  close  contact  with 
a  sheet  of  paper,  and  the  whole  put  out  in  the  light  and  strips 
covered  up  every  thirty  seconds — the  strip  last  covered  just 
showed  a  very  faint  sign  of  light  action.    The  print  was  washed 
and  toned  in  strips,  and  in  baths  of  different  strengths,  and  after 
fixing  three  decided  strips  were  visible  with  increasing  pinkiness. 
This  proves  that  the  paper  must  be  exposed  as  little  as  possible 
to  white  light,  or  there  is  an  action  set  up  which  only  becomes 
visible  in  gold  toning.    When  the  ordinary  baths,  acetate,  borax, 
etc.,  were  strengthened  so  as  to  have  the  strength  of  i£  grs.  of 
gold  to  the  8  oz.,  instead  of  i  gr.,  there  was  less  chance  of  pinki- 
ness.   With  the  matt  papers  as  well  as  the  glossy,  no  bath  works 
so  well  as  the  plain  sulphocyanide,  but  it  is  absolutely  necessary 
to  get  rid  of  all  free  nitrate  and  acid  by  salt  and  washing,  or  else 
the  action  was  uncertain.    Plain  paper  with  uranium  and  gold 
toning  was  a  great  favourite  for  black  tones,  but  with  the  matt- 
gelatine  papers  black  tones  could  not  be  obtained ;  from  this 
bath  we  were  led  on  to  the  others.    Now,  as  to  the  making  of  the 
bath,  I  always  keep  my  gold  in  a  slightly  acid  solution, and  before 
using  it  requires  neutralising.    I  strongly  recommend  also  that 
all  commercial  gold  chlorides  should  be  neutralised  because  one 
well-known  brand  is  very  acid.    The  simplest  way  to  do  it  is  to 
place  a  little  precipitated  chalk  or  magnesium  carbonate  into  the 
gold  solution; »it  requires  very  little  for  one  grain  of  gold,  about 
as  much  as  will  lie  on  a  threepenny  piece ;  shake  well,  then  add 
the  solution  to  the  sulphocyanide.    All  the  sulphocyanides  are 
deliquescent,  and  when  bought  should  be  immediately  dissolved 
in  distilled  water  and  kept  of  a  definite  strength  ;  a  convenient 
one  is  one  in  four.    The  quantity  of  sulphocyanide  compared  to 
the  gold  varies  in  many  formulae,  and  may  vary,  provided  it  is 
more  than  four  times  the  weight  of  the  gold  and  less  than  sixty 
times ;  sulphocyanides  will  dissolve  gelatine  when  too  strong.  A 
convenient  strength  is  gold  chloride  i  grain,  sulphocyanide  30 
grains,  water  8  ounces.    See  that  your  dish  is  clean.    Mix  your 
bath  by  adding  the  gold  to  the  sulphocyanide  gradually  with 
shaking,  not  the  reverse.    Never  mind  the  slight  turbidity  caused 

217 


Gel] 


DICTIONARY  OF  PHOTOGRAPHY. 


by  the  chalk  or  magnesia.  Place  your  well-washed  prints  in  the 
bath,  not  too  many  at  a  time ;  this  is  important.  Keep  them 
moving,  touching  them  with  clean  fingers  at  one  corner  only.  Do 
not  attempt  to  be  economical  of  gold  ;  do  not  tone  more  than 
twelve  quarter-,  six  half-,  or  three  whole-plate  prints  with  one 
grain  of  gold  ;  of  course,  the  number  depends  a  good  deal  on  the 
style  of  the  print.  Finally  keep  your  toning  bath  at  about  650 
F.  Carry  toning  on  till  on  looking  through  the  print  you  see 
that  all  the  red  has  disappeared  from  the  heavy  shadows  for 
purple  tones,  and  till  the  red  has  gone  from  the  half-tones  for 
browns.  When  the  bath  is  used  throw  it  away  or  put  it  in  the 
residue  tank ;  don't  use  it  again,  and  don't  try  and  revive  it  by 
adding  more  gold.  After  toning  place  the  prints  in  salt  and 
water,  and  fix  in  an  alkaline  bath,  and  wash  well  in  running 
water  for  from  twenty  to  thirty  minutes.  Combined  toning  and 
fixing  baths  are  a  great  convenience,  so  it  is  said,  as  by  their  use 
the  number  of  solutions  and  operations  requisite  for  making  a 
print  are  reduced.  I  firmly  believe,  however,  that  there  is  far  less 
chance  of  the  prints  being  permanent  when  treated  with  such  a 
bath  by  the  average  worker.  If  a  combined  bath  is  properly 
made  and  properly  used  there  is  no  reason  why  it  should  not 
yield  as  permanent  results  as  any  other ;  but,  as  ordinarily  used, 
these  baths  are  fatal  to  permanency.  Hyposulphite  of  soda  is 
decomposed  by  acid  and  alum,  and  sulphurous  acid  and  free 
sulphur  are  set  free  and  sulphur  toning  caused.  Although  I  give 
many  formulae  of  combined  baths,  the  only  one  which  I  should 
use  myself  would  be  No.  IX.  For  those  who  must  use  alum  and 
lead  salts  the  following  may  be  adopted : — 

Water         ...       ...       ...       ...       ...  500  parts. 

Hyposulphite  of  soda       ...       ...       ...  200  „ 

Ammonium  sulphocyanide         ...       ...     25  ,, 

Nitrate  of  lead    10  ,, 

Alum   20  ,, 

Dissolve  the  hypo  in  the  water  first,  add  the  sulphocyanide,  then 
dissolve  the  alum  in  a  little  water,  and  add  to  the  hypo,  with 
constant  shaking.  Then  add  the  lead  nitrate  in  the  same  way, 
that  is,  dissolved  in  water,  heat  the  whole  to  500  C.  for  ten 
minutes,  allow  to  cool  and  filter,  and  to  every  100  parts  of  this 

218 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gel 


concentrated  bath  add  100  parts  of  water,  and  7  to  8  parts  of  a 
1  per  cent,  solution  of  gold. 

t. 

Liesegang's  Baths. 
Solution  A. 

Chloride  of  gold    2  grs.  or  •  12  grm. 

Distilled  water    2  ozs.  „  560  c.cm. 

Solution  B. 

Ammonium  sulphocyanide        30  grs.  or    2  grms. 
Hyposulphite  of  soda        ...       1  gr.        06  grm. 
Distilled  water    3  ozs.  „   84  c.cm. 

Mix  for  use  by  pouring  1  part  of  A  into  an  equal  quantity  of 
B  (never  reverse  this  order).    This  gives  a  purplish  tone. 

II. 

The  Phosphate  Bath. 
Solution  A. 

Ammonium  sulphocyanide  1  oz.  or  30  grms. 

Sodium  phosphate  ...       ...       1        ,,    30  ,, 

Distilled  water        ...       ...      25  ozs.  M  700  c.cm. 

Solution  B. 

Chloride  of  gold      ...       ...      15  grs.  or    1  grm. 

Bistilled  water        ...       ...       3  ozs.  ,,  84  c.cm. 

Mix  for  use  by  pouring  1  part  of  B  into  10  parts  of  A.  This 
bath  gives  bluish-black  tones. 

III. 

Solution  A. 

Chloride  of  gold    15  grs.  or       1  grm. 

Distilled  water    60  ozs.  ,,  1,700  c.cm. 

219 


Gel] 


DICTIONARY  OF  PHOTOGRAPHY. 


Solution  B. 

Ammonium  sulphocyanide  I  oz.   or   30  grms. 

Alum   1  ,,      „    30  ,, 

Ammonium  carbonate  ...  4  grs.  „  "25  grm. 
Distilled  water       ...       ...      23  ozs.      500  c.cm. 

For  use,  pour  3  parts  of  A  into  4  parts  of  B,  with  deep  printing. 
This  bath  gives  deep  black  tones.  For  rich  chestnut  brown  with 
no  trace  of  blue,  dilute  the  mixed  bath  with  three  times  the 
quantity  of  water. 

IV. 

A  New  Combined  Toning  and  Fixing  Bath. 

Dr.  Liesegang  recommends  the  following  in  the  International 
Annual,  1889: — 

Solution  A. 

Chloride  of  gold     ...       ...      15  grs.  or    1  grm. 

Distilled  water       ...       ...       3  ozs.  ,,  84  c.cm. 

Solution  B. 

Ammonium  sulphocyanide        60  grs.  or     4  grms. 
Common  salt         ...       ...    240  ,,     ,,  16 

Alum   120  ,,     ,,     8  ,, 

Hyposulphite  of  soda       ...       2  ozs.        62  ,, 
Distilled  water       ...       ...      12   ,,     ,,  350  c.cm. 

Allow  Solution  B  to  stand  for  at  least  eight  days  and  then  filter. 
To  make 

9 

The  Toning  Bath, 

Pour  Solution  A     ...       ...       ...       ...       7  parts 

Into       „       B    60  „ 

and  add  40  parts  of  old  used  combined  toning  and  fixing  bath. 
This  bath  gives  the  prints  in  ten  minutes  a  red  colour,  in  fifteen 
minutes  it  tones  to  a  splendid  brown,  and  in  twenty  minutes  to 
a  brownish  violet.  The  bath  acts  quicker  if  the  prints  are  taken 
out  after  five  minutes  and  laid  on  a  clean  glass  slab.    As  soon 

220 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gel 


as  the  desired  tone  is  reached  place  them  in  a  salt  and  water 
bath. 

V. 

Obernetter's  Baths. 
Solution  A. 

Chloride  of  gold    15  grs.  or    1  grm. 

Distilled  water    3  ozs.  ,,  84  c.cm. 

Solution  B. 

Phosphate  of  Soda   12  drms.  or  43  grms. 

Distilled  water    30  ozs.     „  840  c.cm. 

Solution  C. 

Ammonium  sulphocyanide  10  drms.  or  32  grms. 
Distilled  water      ...        ...     30  ozs.     ,,  840  c.cm. 

For  use  mix  10  parts  of  B  with  10  parts  of  C,  and  add  1  part 
of  A.    This  gives  warm  purplish  tones. 

VI. 
Solution  A. 

Chloride  of  gold                         15  grs.  or  1  grm. 

Distilled  water                           4  ozs.  112  c.cm. 

Solution  B. 

Ammonium  sulphocyanide  5  drms.  or  20  grms. 

Distilled  water       ...       ...      32  ozs.  1  litre. 

For  use,  pour  A  into  B,  and  allow  to  stand  for  twelve  hours. 
This  gives  warm  brown  tones.  The  addition  of  10  to  15  grs. 
of  hyposulphite  of  soda  will  give  cold  tones. 

VII. 
Solution  A. 

Chloride  of  gold    15  grs.  or    1  grm. 

Distilled  water       ...       ...       3  oxs.  „  84  c.cm. 

221 


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DICTIONARY  OF  PHOTOGRAPHY. 


Solution  B. 

Acetate  of  soda    I  oz.   or  31  grms. 

Distilled  water       ...       ...     25  ozs.  „  738  c. cm. 

Solution  A   2  „     ,,    56  ,, 

Solution  C. 

Ammonium  sulphocyanide  2  drms.  or     7  grms. 

Distilled  water    10  ozs.     „  250  c.cm. 

Solution  A    ...       ...       ...       1  oz.  25  „ 

For  use  add  3  parts  of  Solution  C  to  10  parts  Solution  B. 

This  gives  fine  brown  or  black  tones.  Reddish  brown  tones 

maybe  obtained  by  adding  to  Solution  C  10  to  15  grs.  hypo- 
sulphite of  soda. 

VIII. 

The  following  is  a  toning  bath  which  Mr.  Bruce,  of  Duns,  a 
famous  collodio-chloride  printer,  recommended  : — 

Solution  A. 

Ammonium  sulphocyanide         10  drms.  or     40  grms. 
Hyposulphite  of  soda        ...       9  grs.     ,,       -6  grm. 
Distilled  water       ...       ...      60  ozs.     „  1,300  c.cm. 

Solution  B. 

Chloride  of  gold    22  grs.  or     1.5  grm. 

Distilled  water       ...       ...     60  ozs.      1,300  c.cm. 

Add  one  part  of  B  to  an  equal  quantity  of  A,  and  add  a  good-sized 
pinch  of  common  chalk,  and  allow  to  stand  for  twenty-four  hours. 

IX. 

The  following  is  suggested  by  Mr.  Tylar : — 

Chloride  of  gold    6  grs.  or    -4  grm. 

Tungstate  of  soda   60  ,,     ,,     4  grms. 

Ammonium  sulphocyanide  100  ,,     ,,   6-5 .  ,, 

Hyposulphite  of  soda       ...  960  „    ,,  62 

Distilled  water,  to  make   ...  8  ozs.  ,,  200  c.cm. 

Dissolve  the  salts  in  half  the  water  made  hot,  and  make  the  solution 
measure  8  ozs.  by  adding  more  water.    Then  add  the  gold. 

222 


DICTIONARY  OF  PHOTOGRAPHY.  [Gel 


X. 

The  following  is  a  simple  bath  suggested  by  Mr.  W.  K. 
Burton,  although  the  addition  of  nitrate  of  lead  is  due  to  Mr. 
J.  Chester  Jervis  : — 

Chloride  of  gold    6  grs.  or    -4  grm. 

Nitrate  of  lead    3  ,,  *2  ,, 

Hyposulphite  of  soda        ...       3  ozs.  „    93  grms. 

Distilled  water       ...       ...  20  ,,        500  c.cm. 

Put  the  prints  direct  into  the  toning  bath  without  washing. 

Chloride  prints  may  be  easily  developed,  and  by  this  a  great 
saving  of  time  is  effected.  The  first  method  of  doing  this  was 
by  means  of  gallic  acid  developers,  such  a  developer  being 

Gallic  acid    ...      4  parts. 

Citric  acid    ...    6  ,, 

Sodium  acetate    20  ,, 

Solution  of  lead  nitrate  (10  per  cent.)  ...15-20  „ 
Distilled  water    ...       ...  1000  „ 

Warnerke  suggested  the  use  of  about  two  feet  of  magnesium 
ribbon  burnt  quite  close  to  the  printing  frame,  by  which  a  very 
faint  image  was  rendered  visible,  and  it  was  then  developed  to 
full  intensity  with 

Water    ...  ...  ...  1000  parts. 

Acetic  acid   ...  ...      10  ,, 

Sodium  acetate    ...  ...      10  „ 

Gallic  acid    ...       ...       ...  ...  ...       5  ,, 

When  dissolved  add 

Solution  of  lead  acetate  (10  per  cent.)    ...      10  parts. 

The  above  solution  should  be  diluted  with  from  5  to  10  parts  of 
water,  and  the  print,  without  washing,  being  placed  in  this  soon 
gains  in  intensity,  and  the  development  is  stopped  by  placing  the 
print  in  salt  and  water,  when  it  should  be  thoroughly  well  washed 
and  toned  in  the  following  bath  : — 

Water          ...       ...       ...       ...       ...  1000  parts. 

Hyposulphite  of  soda        ...       ...       ...  100  ,, 

Acetate  of  lead    10 

Solution  of  chloride  of  gold  (1  per  cent.)...  20  ,, 
223 


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DICTIONARY  OF  PHOTOGRAPHY. 


Valenta  suggested  the  use  of  acid  hydroquinone  and  pyrogallol 
developers. 

Hydroquinone  Developer. 

A.  Hydroquinone    10  parts. 

Alcohol    ioo  „ 

B.  Sodium  sulphite      ...       ...       ...       ...    ioo  parts. 

Distilled  water       ...       ...       ...       ...  500 

Citric  acid   5 

For  use,  50  parts  of  Solution  A  should  be  mixed  with  50  parts  of 
Solution  B,  and  1000  parts  of  water  added. 

Pyrogallol  Developer. 

Distilled  water    1000  parts. 

Sodium  sulphite      ...       ...       ...       ...  100  „ 

Pyrogallol    10  ,, 

Citric  acid    11  ,, 

The  ingredients  should  be  dissolved  in  the  water  in  the  above, 
and  the  clear  and  almost  colourless  solution  used  immediately. 
The  hydroquinone  developer  works  clear  and  slowly  ;  the  violet 
tone  of  the  printed-out  image  turns  in  developing  into  a  yellowish- 
brown.  The  prints  were  toned  and  fixed  in  the  combined  toning 
and  fixing  bath  composed  as  follows : — 

Distilled  water    500  parts. 

Hyposulphite  of  soda        ...       ...       ...  200  „ 

Sulphocyanide  of  ammonia         ...       ...  25  ,, 

Alum   30  „ 

Acetate  of  lead  solution  (1  :  10)   40  ,, 

This  solution  is  to  be  heated  on  a  water  bath  to  about  6o°  C, 
by  which  a  quick  deposition  of  the  precipitate  formed  is  obtained. 
It  should  then  be  filtered,  and  100  parts  of  it  mixed  with  50  parts 
of  water  and  10  parts  of  1  per  cent,  solution  of  choride  of  gold. 
In  this  combined  bath  the  yellowish-brown  developed  prints 
assume  a  yellow  tone,  which  very  soon  turns  into  brownish-red, 
and  into  a  beautiful  deep,  purple  brown.  The  toning  process 
should  be  stopped  when  the  prints  have  assumed  the  desired 
tone,  and  it  should  be  noted  that  after  washing  the  tone  is 
rather  deeper.  Liesegang  specially  recommends  the  following 
for  his  own  paper,  but  for  others  it  is  not  suitable  : — 

224 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gel 


A.    Pyrogallol  Developer. 

Solution  of  pyro  (7  per  cent.)    2  parts. 

„      „  sodium  acetate  (20  per  cent.)  6 

Distilled  water    60  „ 

B.    Paramidophenol  Developer. 

Solution  of  paramidophenol  (7  per  cent.)  2  parts. 

if  sodium  acetate  (20  per  cent.)  10  „ 

Citric  acid    ...  ...       ...       ...  1 

Distilled  water    ...       ...  50  „ 

The  greatest  advance  in  this  process  was  made  by  Mr.  Wilson, 
of  the  Paget  Prize  Plate  Co.,  when  he  suggested  the  use  of  a 
solution  of  potassium  bromide  prior  to  development.  The  follow- 
ing is  the  precise  method  of  working  this  modification  of  the 
process  : — The  paper  should  be  exposed  in  the  printing  frame  in 
the  ordinary  way,  but  the  insolation  is  only  continued  till  there 
is  quite  a  faint  image.  It  is  advisable  not  to  print  too  far,  and 
as  a  good  guide  we  may  suggest  that  the  details  should  just  be 
visible  in  the  half-tones.  After  printing,  the  paper  should  be 
taken  from  the  frame,  and  placed  without  washing  into  a  10  per 
cent,  solution  of  potassium  bromide.  The  action  of  this  bath  is 
to  convert  the  soluble  silver  salts  into  silver  bromide,  and  if 
allowed  to  act  for  some  time,  there  is  no  doubt  it  would  also 
replace  the  chlorine  in  the  silver  salt  forming  the  image.  The 
time  of  immersion  in  the  bromide  solution  is  not  very  material, 
and  we  prefer  to  leave  it  for  fifteen  minutes.  Great  care  must 
be  taken  that  no  bubbles  adhere  to  the  paper,  or  else  spots  will 
appear  in  the  development.  After  being  in  the  bromising  solu- 
tion the  prints  must  be  washed  well  for  five  or  ten  minutes  in 
running  water ;  if  the  washing  is  not  pretty  complete  and  thorough, 
so  much  bromide  is  left  in  the  paper  that  development  is  enor- 
mously protracted,  and  there  is  a  tendency  to  stain.  The  original 
developer  recommended  was — 

I. 


Hydroquinone 

h  oz. 

Sulphurous  acid 

1 

4  M 

Sodium  sulphite 

1 

t  II 

Potassium  bromide... 

6o  grs. 

Water,  to 

...      25  „ 

225 

Q 

Gel] 


DICTIONARY  OF  PHOTOGRAPHY. 


II. 

Caustic  soda   ...       ...       ...       £  oz. 

Sodium  sulphite      ...       ...    ^  ,, 

Water,  to    25  ozs. 

III. 

Ammonium  bromide         ...    1  oz. 

,,        carbonate       ...  ...       ,,.       1  ,, 

Distilled  water,  to  ...       ...  ...       ...  25  ozs. 

Mix  in  equal  parts.  The  following  simpler  developer  is  now 
suggested : — 

I. 

Hydroquinone        ...       ...  ...       ...  1  oz. 

Sodium  sulphite      ...       ...  ...       ...  1  ,, 

Sulphurous  acid      ...       ...  ...       ...  ^  ,, 

Water,  to    40  ozs. 

II. 

Potassium  bromide ...       ...       ...       ...  i\  ozs. 

Liq.  ammonia  (8-8o)         ...       ...       ...  180  m. 

or 

Sodium  carbonate  ...       ...       ...       ...  2  ozs. 

Water,  to    40  ,, 

For  use,  mix  one  part  of  each,  and  add  one  part  of  water.  For 
average  negatives,  use  one  part  No.  I.,  one  part  No.  II.,  one  part 
water.  Whatever  variations  are  made,  make  up  always  to  bulk 
three  parts,  by  adding  or  omitting  water.  If  required  to  work 
slower,  use  less  No.  II.,  or  make  up  the  stock  solution  with  less 
ammonia.  If  harder  effect  (more  contrast)  be  desired,  use  less 
No.  I. ;  if  softer  results  (less  contrast),  use  more.  It  may  happen 
that  we  find  that  the  print  when  finished  is  too  dark,  and  has 
been  over-printed.  The  question  is  how  to  reduce  it.  It  is 
questionable  whether  it  is  worth  the  trouble,  whether  it  is  not 
almost  as  easy  to  make  a  fresh  print  altogether.  The  old  ferrid- 
cyanide  and  hypo  reducer  has  been  suggested  for  gelatino-chloride 
prints  ;  and  reduce  them  it  will,  so  energetically,  even,  in  weak 
solutions  that  its  action  is  uncontrollable.  Whilst  talking  of  this 
reducer  it  may  not — in  fact  it  does  not  seem  to — be  generally 

226 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gla 


known  that  it  will  totally  remove  even  a  gold-toned  image,  and  as 
the  image  disappears  entirely  it  must  be  assumed  that  the  gold 
is  also  dissolved.  Haddon  suggested  a  mixture  of  sulphocyanide 
and  ferridcyanide,  and  this  certainly  acts  more  slowly  and  evenly, 
but  the  sulphocyanide  makes  the  gelatine  very  soft.  Valenta 
suggests,  however,  a  mixture  of  hypo  and  uranium  nitrate,  and 
states  that  it  gives  very  good  results.  He  suggests  a  cold  satu- 
rated solution  of  hypo  diluted  with  four  times  the  quantity  of 
water,  and  to  every  100  parts  of  this  liquid  one  part  of  a  10  per 
cent,  solution  of  uranium  nitrate  is  added.  This  acts  very  evenly 
and  slowly,  and  gives  excellent  results,  as  we  can  testify.  Valenta 
states  that  prints  treated  with 

Thiosinamin   5  parts 

Water    100  ,, 

Solution  of  uranium  nitrate  (10  per  cent)  5-10 

assume  a  brilliant  red  tone,  which  gives  place  in  toning  to  a  rich 
sepia.  All  chloride  papers  can  be  toned  with  platinum,  by  ob- 
serving the  directions  given  under  Platinum  Toning  (r/.v.).  Since 
the  introduction  of  matt-surface  chloride  papers  there  has  not  been 
so  much  need  for  obtaining  matt  surfaces  on  glossy  papers ;  but 
this  can  be  done  either  by  rubbing  down  the  dry  print  with 
powdered  pumice  stone  or  squeegeeing  to  fine  ground-glass  or 
celluloid,  both  of  which  should  be  previously  smeared  with  a 
little  oil.  To  obtain  a  high  glaze  or  polish,  plate-glass,  ebonite, 
metal  plates,  or  wood-pulp  slabs  can  be  used,  but  the  first  gives 
the  finest  surface.  Whichever  material  is  used,  it  should  be  first 
rubbed  with  solution  of  wax,  as  used  for  the  carbon  tissue,  en- 
caustic paste,  or  a  little  oil,  and  the  wet  print  well  squeegeed 
down  to  it  and  allowed  to  dry,  and  then  stripped.  For  mounting 
such  prints  it  is  advisable  to  paste  on  the  back  a  sheet  of  the 
waterproof  backing-paper,  which  can  be  obtained  commercially, 
whilst  the  print  is  damp,  and  allowing  the  two  to  dry  together, 
and  then  mounting  with  one  of  the  gelatine  mountants,  now 
placed  on  the  market,  or  a  formula  for  which  is  given  under 
Mountant  (q.v.). 

Glass.  A  transparent  brittle  substance,  now  of  universal 
occurrence  and  application.  Its  origin  is  uncertain.  It  was 
known  to  the  Egyptians  5000  to  6000  years  ago.    The  earliest 

227 


Gla]  DICTIONARY  OF  PHOTOGRAPHY. 

specimen  known  is  a  small  tablet  in  the  British  Museum,  of 
about  1445  B.C.,  of  Egyptian  make ;  it  is  opaque  and  coloured. 
There  is  also  a  goblet  found  in  Nineveh,  of  about  700  B.C., 
the  earliest  piece  of  any  size.  The  manufacture  was  gradually 
improved,  till,  in  Italy,  58  B.C.,  the  theatre  walls  in  some  towns 
were  ornamented  with  mirrors,  and  at  Pompeii  windows  which 
were  glazed  have  been  found  intact.  About  a.d.  674  the  art 
of  glass-making  was  introduced  into  England,  and  it  is  now 
carried  on  at  Newcastle,  Liverpool,  Bristol,  Birmingham,  Leeds, 
London,  Glasgow,  and  other  places.  Some  of  the  lens  glass  is 
imported  from  abroad.  There  are  many  kinds  of  glass,  but  only 
one  or  two  of  any  interest  to  photographers.  Crown  and  flint 
are  the  kinds  used  for  lenses,  while  for  the  best  dry  plates  an 
inferior  plate  is  used.  Crown  glass  is  composed  of  a  mixture 
of  silicates  of  potash  (K203Si02),  lime  (Ca203Si02),  and  alumina 
(Al203Si02).  It  has  specific  gravity  2-487.  Flint  glass  is  a  mix- 
ture of  silicates  of  potash,  alum,  and  lead  (Pb202Si02).  It  has 
specific  gravity  3-5-  It  is  much  more  refractive  than  crown. 
Crystal  glass  is  an  extremely  pure  variety  of  glass,  and  is  the  one 
generally  used  for  the  finer  lenses.  Glass  can  be  coloured  by  fusing 
metallic  oxides  with  it.  Gold  and  copper  give  red,  silver  or  iron 
green,  uranium  yellow,  cobalt  blue  colours.  When  the  glass  is 
coloured  throughout  it  is  called  "pot  metal."  Another  method 
of  colouring  is  by  attaching  an  extremely  thin  sheet  of  pot  metal 
to  white  glass,  when  it  is  known  as  "  flashed  glass.''  Opal  glass 
is  made  by  fusing  with  the  metal  one  of  the  oxides  of  tin  or  zinc. 
In  the  manufacture  of  crown,  flint,  and  crystal  glass  for  optical 
purposes  extreme  care  is  taken  to  make  the  resulting  glass  non- 
hygroscopic,  or  non-absorbent  of  water,  to  which  some  glass  is 
particularly  liable,  also  to  obtain  it  absolutely  free  from  bubbles 
and  striae,  the  latter  being  lines  due  to  imperfect  mixing  of  the 
molten  metal.  (See  Lens.)  In  1881  Drs.  Abbe  and  Schott 
instituted  a  series  of  experiments  at  Jena,  in  Germany,  on  the 
improvement  of  the  manufacture  of  glass  for  optical  purposes, 
and,  after  some  successful  trial  smeltings,  in  1884  they  received 
a  handsome  subsidy  from  the  Prussian  Bureau  of  Education, 
which  enabled  them  to  commence  operations  on  a  manufacturing 
scale.  The  old  optical  glasses  were  limited  to  practically  few 
varieties,  which  were  characterised  by  the  dispersion  always 
being  in  a  certain  relation  to  the  mean  refractive  index,  so  that 

228 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gol 


a  higher  index  of  refraction  was  accompanied  by  a  greater  dis- 
persion, and  vice  versa.  This  limited  the  optician  considerably 
in  his  work,  and  entailed  a  certain  residuum  of  errors  in  correc- 
tion of  chromatic  and  spherical  aberrations,  which  were  unavoid- 
able. The  Jena  glass,  by  the  introduction  of  new  elements  into 
its  composition,  has  been  obtained,  not  only  with  all  the  charac- 
teristics of  the  old  glass,  but  also  with  quite  the  opposite 
characters — that  is  to  say,  with  high  index  of  refraction  and  low 
dispersion,  and  vice  versa.  To  enter  fully  into  the  method  of 
manufacture,  and  all  the  theoretical  considerations  involved, 
would  be  beyond  the  scope  of  this  work ;  but  the  practical  out- 
come of  the  introduction  of  these  glasses  has  been  considerable 
improvement  in  the  manufacture  of  the  old  type  of  lenses,  and 
many  new  and  improved  lenses,  such  as  the  Ross  Concentric, 
the  Zeiss  anastigmats,  and  the  double  anastigmat  of  Goerz. 

Glucose  (Ger.,  Glucose,  Starkezitcker,  Traubenzucker ;  Fr., 
Glucose;  Ital.,  Glucosid).  Synonyms:  Grape  Sugar,  Dextrose. 
C6H,.,06=i8o.  There  are  several  kinds  of  glucose,  which  is 
preferably  to  be  considered  as  a  generic  name.  It  occurs  either 
in  white  crystals  or  a  thick,  syrupy  liquid,  and  was  used  as  a 
preservative  in  the  collodion  process,  and  also  in  some  powder 
processes. 

Glycerine  (Ger.,  Glycerin;  Fr.,  Glycerine;  Ital.,  Glicerina ; 
Lat.,  Glycerinuin).  Synonyms:  Glycerol,  Propenyl  Alcohol.  C3 
H803=92,  or  C3H5(OH)3.  A  peculiar,  sweet,  viscid  liquid 
obtained  from  oils  and  fats  by  saponification  and  subsequent 
purification.  Specific  gravity,  1-260.  It  is  extremely  hygro- 
scopic, and  cannot  be  dried  by  heat  without  decomposition.  Its 
non-drying  properties  are  taken  advantage  of  in  photography  to 
prevent  the  too  rapid  drying  of  some  substances,  and  it  is  also 
used  as  a  preservative  of  pyro.  It  is  miscible  in  all  proportions 
with  water  and  alcohol.  It  has  also  been  suggested  as  a  re- 
strainer  in  developing,  its  action  being  purely  physical  in  this 
sense. 

Gold  (Ger.,  Gold;  Fr.,  Or;  Ital.,  Oro ;  Lat.,  Auruni).  Au. 
=  196-6.  A  yellow  or  yellowish-red  metal  soluble  only  in  nitro- 
hydrochloric  acid.  It  occurs  native  in  conjunction  with  quartz 
and  sand  in  various  parts  of  the  world.    It  is  used  for  the  pre- 

229 


Gol] 


DICTIONARY  OF  PHOTOGRAPHY. 


paration  of  chloride  i  oft  gold,  a  convenient  source  being  current 
coin,  particularly  Australian  sovereigns  and  old  jewellery.  A 
sovereign  should  weigh  when  new  123^  grains,  and  contain  113 
grains  of  pure  gold. 

Gold,  Chloride  (Ger.,  Goldchlorid,  Chlorgold;  Fr.,  Chlorure 
d'oro;  Ital,  Chloruro  d'oro).  Synonyms:  Auric  Chloride, 
Trichloride  or  Perchloride  of  Gold.  AuCl3=303.  A  yellowish- 
brown  crystalline  mass,  made  by  dissolving  gold  in  aqua  regid. 
Usually  commercial  chloride  is  obtained  by  solution  as  above 
and  the  evaporation  of  the  acid  liquid,  in  which  case  bright  yellow 
crystals  of  AuCl3HCl  are  obtained,  from  which  it  will  be  seen 
that  one  equivalent  of  hydrochloric  acid  is  combined  with  it. 
Preferably  the  double  neutral  salts  of  gold  and  potassium,  sodium 
or  calcium  are  used. 

Gold,  Potassio-Chloride  (Ger.,  Chlorgoldkalium ;  Fr., 
Chlorure  double  d'or  et  de  potassium ;  Ital,  Chloruro  doppio 
d'oro  e  di  potassio).  AuCl3KCl  +3H20  =  4I3.  The  usual 
method  of  making  this  is  to  dissolve  one  part  of  pure  gold  in  as 
small  a  quantity  of  aqua  regid  as  possible,  by  the  aid  of  heat. 
Evaporate  gently,  and  then  add  20  parts  of  distilled  water,  in 
which  0-51  parts  of  bicarbonate  of  potassium  has  been  dissolved. 
Carbonic  acid  is  given  off,  and  the  resulting  solution  should  be 
evaporated  to  dryness.  Lainer  of  Vienna  has  also  suggested 
the  following  method  for  obtaining  a  stable  and  constant  salt  of 
gold,  which  can  easily  be  prepared  chemically  pure  and  free 
from  acid,  which  does  not  deliquesce  or  effloresce,  and  gives 
toning  baths  of  constant  and  reliable  action.  One  hundred  parts 
of  gold  are  dissolved  in  aqua  regid,  and  hydrochloric  acid  added 
to  the  solution.  To  the  solution  of  pure  chloride  of  gold  thus 
prepared  are  added  38  parts  of  chloride  of  potassium.  The 
mixture  thus  obtained  is  carefully  evaporated  till  crystallisation, 
when  the  dish  or  vessel  is  placed  under  a  bell  jar  containing 
concentrated  sulphuric  acid  or  quicklime.  The  mother  liquid  is 
poured  off,  and  this  again  evaporated  and  treated  as  above.  The 
crystals  thus  obtained  are  dried  under  a  bell  jar,  and  heated  to 
100 — no°  C.  to  drive  off  the  remaining  traces  of  free  hydro- 
chloric acid.  The  salt  thus  procured  forms  yellow  hexagonal 
needles,  easily  soluble  in  water. 

230 


DICTIONARY  OF  PHOTOGRAPHY. 


[Gra 


Gold,  Sodio-Chloride  (Ger.,  Chlorgoldnatrium ;  Fr.,  Chlorure 
double  d'or  etde  sodium;  Ital.,  Chloruro  doppio  d'oro  e  di  sodio. 
AuCl3NaCl+2H.,0=397.  This  is  usually  the  commercial  salt,  and 
occurs  as  yellowish-brown  needles,  which  are  very  deliquescent, 
soluble  in  alcohol  and  water.  It  may  be  prepared  by  dissolving 
5  parts  by  weight  of  gold  chloride,  and  I  part  by  weight  of  sodium 
chloride  in  as  little  water  as  possible,  and  allowing  the  solution 
to  crystallise.  Another  method  is  to  dissolve  I  part  of  gold  in 
10  parts  of  aqua  regid  by  the  aid  of  heat,  dilute  with  100  parts 
of  water,  filter  through  glass  wool,  precipitate  the  gold  with 
saturated  solution  of  sulphate  of  iron,  and  collect  and  wash  the 
precipitate,  which  is  pure  gold ;  add  3  parts  of  sodium  chloride 
to  every  1  of  gold  ;  dissolve  the  mixture  in  aqua  regid  and 
evaporate.  The  following  table  shows  the  equivalent  quantities 
of  the  various  salts  used  in  photography  : — 


Gold. 

Gold 

Gold 

Gold 

Chloride. 

Potassio-Chloride. 

Sodio-Chloride. 

1-5420 

2-1048 

2-0229 

0-6485 

I 

I-3645 

I-3II9 

0-475I 

0*7326 

I 

0-961 1 

o-4943 

0-7623 

I  -0405 

I 

The  following  calculation  will  show  that  home-made  chloride  is 
cheaper  than  commercial.  An  Australian  sovereign  contains 
H3grs.  of  pure  gold,  which  will  make  174^  grs.  of  pure  chloride, 
237-9  grs.  of  potassio-chloride,  and  228-6  grs.  of  sodio-chloride, 
and,  assuming  that  the  latter  be  the  commercial  salt,  this  is 
equivalent  to  15^  tubes. 

Gold,  Hyposulphite  (Ger.,  NatriumaurotJiiosulfat,  Unter- 
schwefligsdures  Goldoxydulnatron ;  Fr.,  Hyposuljite  double  d'or 
et  de  sodium;  Ital.,  ipolsolfito  d'oro  e  di  sodio).  Synonyms: 
Sel  dor,  Fordos  and  Gelis'  salt.  3Na2S203,Au,S_X)3,4HaO  =  io5o. 
This  salt  was  originally  suggested  for  toning  daguerrotypes,  and 
later  for  albumenised  paper,  and  more  recently  still  for  gelatino- 
chloride  paper.  It  may  be  formed  by  gradually  adding  a  neutral 
2  per  cent,  solution  of  chloride  of  gold  to  a  6  per  cent,  solu- 
tion of  hyposulphite  of  soda.  To  obtain  it  in  crystals,  mix  the 
solution  formed  above  with  alcohol,  when  the  salt  will  crystallise 
out  in  fine  white  needles. 

Grain.    See  Weights  and  Measures. 

231 


Gra] 


DICTIONARY  OF  PHOTOGRAPHY. 


Gramme.    See  Weights  and  Measures. 
Green  Fog.   See  Fog. 
Ground-Glass.   See  Focus. 

Gum  Arabic  (Ger.,  Gummi  arabicum,  Arabische  Gummi ; 
Fr.,  Gomme  arabique ;  ltal.,Gomma  arabicd).  A  gummy  exuda- 
tion from  the  stems  of  various  species  of  acacia.  It  is  of  peculiar 
bland  taste,  odourless,  insoluble  in  alcohol  and  ether,  but  entirely- 
soluble  in  water,  in  which  form  it  is  used  as  a  Mountant  (q.v.). 
It  is  also  used  in  the  powder  process  and  photo-lithography.  Its 
adhesiveness  is  increased  by  addition  of  aluminium  sulphate,  less 
so  by  ordinary  alum.  It  is  decomposed  at  a  temperature  of  300°* 
and  is  converted  into  dextrine  by  the  action  of  sulphuric  acid. 

Gum  Dammar.   See  Dammar. 

Gum  Dragon.   See  Tragacanth. 

Gum  Elemi  (Ger.,  Oelbaumharz :  Fr.,  Gomme  elemi.)  A 
resinous  exudation  from  Canarium  commune,  imported  from  the 
Philippine  Islands,  and  also  obtained  from  Amyris  elemifera  in 
Central  America.  It  is  used  in  varnishes  and  encaustic  paste.  It 
is  very  soluble  in  alcohol,  insoluble  in  water,  and  should  have 
somewhat  the  colour  and  consistence  of  honey,  but  generally, 
from  exposure  to  air  and  impurities,  is  more  yellowish-brown. 

Gum  Guaiacum.  A  resinous  exudation  from  Guaiacum 
officinale,  a  native  of  San  Domingo  and  Jamaica,  soluble  to  the 
extent  of  90  per  cent,  in  absolute  alcohol,  and  when  triturated 
with  water  forms  a  mucilage  of  pale  greenish  hue.  It  is  used  in 
some  of  the  old  collodion  processes. 

Gun-Cotton.    See  Pyroxyline. 

Halation.  A  blurring  of  the  image  and  an  encroachment  of 
the  high-lights  upon  the  surrounding  shadows  or  darker  portions. 
It  is  but  too  well  known  as  the  defect  of  photographing  an 
interior  in  which  a  brilliantly  lighted  window  appears  ;  or  again, 
when  photographing  landscapes  in  autumn  or  winter,  halation  is 
very  likely  to  make  its  appearance  when  the  leafless  boughs  of 
the  trees  appear  against  a  bright  sky,  or  in  any  case  where 
extreme  contrasts  of  light  and  shade  exist.  It  is  caused  by 
reflection  from  the  back  of  the  plate.  The  rays  of  light  are 
scattered  by  the  particles  of  silver  salt,  and,  obeying  certain 

232 


DICTIONARY  OF  PHOTOGRAPHY. 


[Har 


laws  of  reflection,  are  reflected  from  the  surface  and  back  of 
plate.  The  remedies  are  Backing  the  Plate  (g.v.),  the  use  of 
thickly-coated  and  matt-surfaced  plates,  and  plates  containing 
iodide  of  silver,  the  latter  being  an  almost  certain  preventative 
of  halation,  chiefly  because  the  iodide  emulsion  is  more  opaque 
than  a  bromide  ;  but  if  an  emulsion  could  be  obtained  absolutely 
transparent,  there  would  be  practically  no  halation.  When 
photographing  interiors,  it  has  been  recommended  to  cover  the 
window  with  some  slightly  opaque  substance,  such  as  pale  yellow 
linen  or  unbleached  calico,  so  as  to  reduce  the  intensity  of  the 
light  ;  and,  again,  it  has  been  recommended  to  cut  small  shapes 
of  black  velvet,  and  hang  on  wires  in  front  of  the  camera,  so  as  to 
exclude  the  windows  themselves  from  the  focussing  screen,  re- 
moving them  only  a  short  period  before  the  close  of  exposure. 
When  halation  does  not  exist  in  a  negative,  local  Reduction  (q.v.) 
may  be  resorted  to,  or  the  process  described  under  Harmonising 
Harsh  Negatives  (q.v.)  may  be  used  with  great  success,  or  the 
dense  deposit  may  be  partially  removed  by  careful  rubbing  down 
with  wash-leather  and  methylated  alcohol. 

Half-Plate.  The  size  of  dry-plate  6}2  by  4$  The  true  half- 
plate  is  6£  by  4|. 

Halogens.  This  term  has  been  applied  to  the  group  of  the 
four  elements,  chlorine,  bromine,  iodine,  fluorine,  which  are 
closely  connected  by  similarity  of  their  chemical  properties,  and 
the  term  has  arisen  from  their  forming  salts  closely  allied  to 
sea  salt,  and  the  salts  thus  formed  are  called  haloids. 

Harmonising  Harsh  Negatives.  This  process  is  a  very 
valuable  one,  and  should  be  far  more  frequently  used  than  it  is. 
It  will  reduce  the  dense  parts  of  a  harsh  negative  and  intensify 
weak  parts.  By  means  of  this  process  it  is  possible  to  obtain  a 
really  decent  print  from  a  negative  of  a  church  interior  which  is 
almost  a  mass  of  halation,  and  passable  prints  may  be  obtained 
from  harsh  under-exposed  negatives.  It  was  suggested  first  by 
Eder  in  1883.  The  negative,  after  being  fixed  and  well  washed, 
should  be  soaked  in  a  solution  of 

Potassium  bichromate       ...       ...       ...        1  part. 

Hydrochloric  acid    ...       ...       ...       ...      3  parts. 

Alum   ...       ...       ...  5 

Water   100  M 

233 


Har] 


DICTIONARY  OF  PHOTOGRAPHY. 


In  this  the  negative  gradually  turns  white,  and  care  must  be 
exercised  that  it  is  thoroughly  bleached  from  the  back  as  well 
as  the  front.  The  negative  must  now  be  thoroughly  washed 
in  running  water  for  at  least  two  hours,  or  repeated  soaking, 
film  downwards,  in  frequently  changed  water  for  at  least  four 
hours.  The  bleached  plate  may  now  be  redeveloped,  either 
with  an  old  hydroquinine  developer  or  with  ferrous  oxalate. 
This  is  the  important  point  in  this  process,  for  development 
must  only  be  carried  on  till  the  details  in  the  shadows  are  fully 
developed,  and  not  till  the  high  lights  are  developed  right 
through,  or  in  the  latter  case  no  improvement  will  be  seen.  As 
soon  then  as  the  details  in  the  shadows  and  half-tones  are 
developed,  the  plate  may  be  rinsed  and  refixed.  There  being 
still  some  undeveloped  chloride  of  silver  at  the  back  of  the  dense 
parts,  this  is  fixed  out,  and  the  negative  will  be  found  by  no 
means  so  hard  as  before.  I  have  stated  that  this  process  in- 
tensifies the  shadows,  and  this  is  only,  strictly  speaking,  true 
when  the  bleached  plate  is  exposed  to  daylight  for  some  time 
and  then  developed,  the  chloride  of  silver  image  then  being  con- 
verted into  a  more  nonactinic  character  than  previously.  An 
alternative  method  due  to  Mr.  J.  Mcintosh  is  the  following. 
Prepare  the  following  solution  : — 

Bichromate  of  potassium   ...       ...       ...    10  grs. 

Bromide  of  potassium       ...       ...       ...     5  ,, 

Water    1  oz. 

Bathe  the  plate  and  allow  the  solution  to  permeate  the  film. 
Pour  the  solution  off  and  add  to  it  five  drops  of  nitric  acid. 
Again  flood  the  plate  and  the  image  will  be  converted  into 
bromide  of  silver.  Allow  the  action  to  proceed  through  the 
film.  Bathe  in  three  changes  of  alum,  a  5  per  cent,  solution 
of  potassium  metabisulphite,  to  remove  the  bichromate  and 
harden  the  film,  and  wash  thoroughly  in  water.  As  the  opera- 
tions are  carried  out  in  white  light,  such  as  that  of  gas  or  a  lamp, 
the  plate  is  amply  exposed  by  the  time  the  washing  is  completed. 
The  following  pyro  developer  was  found  quite  suitable.  Any 
preservative  may  be  used,  but  as  there  is  nothing  on  the  plate 
but  the  image  to  be  affected  by  the  developer,  there  is  no 
necessity  to  use  a  bromide.    A  small  trace  may  be  useful  to 

234 


DICTIONARY  OF  PHOTOGRAPHY.  [Har 

control  development,  but  if  any  bichromate  of  potassium  remains 
in  the  film  it  will  unite  with  the  bromide,  and  convert  the  image 
back  into  bromide  of  silver  as  fast  as  it  developed. 

Pyro  2  grs. 

Ammonia   2  mins. 

Bromide  of  potassium  (if  used  at  all)     ...    £  gr. 

As  the  shadow  detail  lies  on  the  surface  it  will  first  be  developed, 
the  half-tone  will  follow,  and  the  high  lights  will  remain  white 
when  viewed  from  the  back  of  the  plate  for  some  time.  As  the 
surface  of  the  film  will  veil  over  as  soon  as  the  developer  begins 
to  act,  the  progress  must  be  judged  entirely  from  the  back  of  the 
plate.  The  only  judgment  required  in  the  process  is  in  stopping 
the  development  at  the  right  time.  If  stopped  too  soon,  the 
negative  will  be  flat ;  if  carried  too  far,  the  negative  will  still  be 
hard.  Mr.  Mcintosh  says :  "  It  will  be  well  to  have  ready  for 
reference  a  print  from  the  negative  in  which  the  shadows  have 
been  printed  to  their  proper  depth.  When  the  lightest  half- 
tone which  shows  in  the  print  is  nearly,  but  not  quite,  blackened 
through  by  the  developer,  on  viewing  the  plate  from  the  back  the 
action  should  be  stopped,  the  plate  washed  and  transferred  to 
the  hypo,  which  will  speedily  dissolve  out  the  undeveloped  silver 
in  the  high  lights,  leaving  the  negative  much  thinner  in  the  high 
lights  than  it  originally  was.  A  little  practice  with  waste 
negatives  will  give  the  required  power  of  judgment.  A  negative 
which  is  hard  from  under-exposure,  and  one  which  has  been 
fuHy  exposed  but  is  hard  from  over-development,  will  not  present 
the  same  appearance  during  redevelopment,  after  rehalogenis- 
ation.  If  the  former  be  redeveloped  right  through,  the  high 
lights  will  appear  black  at  the  back  of  the  plate,  the  high  light 
in  the  fully  exposed  negative  will  never  appear  black,  however 
far  the  redevelopment  may  be  pushed,  and  as  the  layer  of 
white-coloured  silver  present  in  this  case  will  not  be  dissolved 
out  by  the  hypo,  an  allowance  for  this  must  be  made  in  re- 
development, or  the  negative  will  still  be  too  dense.  There  is 
no  theoretical  objection  to  the  negative  being  again  treated  by 
the  process  to  obtain  the  required  reduction,  but  in  practice 
there  is  an  additional  risk  of  stains  appearing  the  second  time. 
It  is  better  to  err  on  the  side  of  under-development  and  intensify 

235 


Hea] 


DICTIONARY  OF  PHOTOGRAPHY. 


if  necessary.  In  this  process,  as  in  all  others,  great  cleanliness 
is  required,  and  the  plate  must  have  been  thoroughly  freed  from 
hypo  before  proceeding  to  rehalogenise.  If  hypo  or  other 
chemicals  be  present,  thin  patches  and  dark  spots  will  show. 
If  there  are  grease-spots  or  finger-marks  on  the  plate,  irregular 
action  will  take  place.  It  is  best  to  take  but  one  trial  print 
from  the  negative,  and  exercise  great  care  in  doing  so  if  re- 
halogenisation  be  thought  needful.  When  operating  on  old 
negatives  I  wash  them  gently  with  dilute  ammonia  to  get  rid  of, 
if  possible,  grease-spots  before  beginning  the  process." 

Head-Rest.  An  apparatus  used  for  maintaining  an  exact 
position  and  steadiness  of  a  sitter  during  exposure.  Great 
prejudice  exists  in  the  minds  of  most  people  against  it,  due  to 
its  use  having  been  abused  to  such  an  extent  as  to  become  an 
absolute  instrument  of  torture.  In  all  cases  the  head-rest  should 
be  brought  to  the  sitter's  head,  and  applied  fgently,  so  as  to  give 
sufficient  support  without  giving  any  idea  of  rigidity. 

Hectogramme.   See  Weights  and  Measures. 
Hectolitre.   See  Weights  and  Measures. 
Hectometre.   See  Weights  and  Measures. 
Heliochromy.   See  Photography  in  Natural  Colours. 
Heliotype  Process.   See  Collotype. 

High-Lights.  The  brightest  parts  of  a  picture,  which  are 
represented  by  the  greatest  density  or  opacity,  in  the  negative, 
as  the  face  in  portraits,  the  sky  and  other  bright  portions  in 
the  landscape. 

History  of  Photography.   See  Photography. 

Hydriodic  Acid  (Ger.,  Iodwasserstoffsaure ;  Fr.,  Acide 
iodhydrique;  Ital.,  Acido  iodidrico).  HI=I28.  Made  in  a  some- 
what similar  method  to  hydrobromic.  It  forms  salts  called 
iodides. 

Hydrobromic  Acid  (Ger.,  Bromwasserstoffsaure ;  Fr.,  Acide 
hydrobro?nique ;  Ital.,  Acido  idrobromico).    HBr=8i.    Is  made 

236 


DICTIONARY  OF  PHOTOGRAPHY. 


[Hyd 


either  by  decomposing  potassium  bromide  with  tartaric  acid  or 
by  passing  sulphuretted  hydrogen  through  bromine  water.  It 
forms  salts  termed  bromides  in  which  form  alone  it  is  used  in 
photography. 

Hydrochloric  Acid  (Ger.,  Chlorwasserstoffsaure ;  Fr.,  Acide 
chlorhydrique  ;  Ital.,  Acido  chloridricd).  HCl=36-5.  Synonyms: 
Muriatic  acid,  Spirits  of  salts.  Made  by  roasting  salt  in  furnaces 
with  sulphuric  acid.  Specific  gravity  ri6o.  Its  use  is  limited 
to  the  clearing  bath,  and  combined  with  nitric  acid  to  make 
chloride  of  gold.  It  combines  with  alkalies  and  basylous  radicles 
to  form  chlorides. 

Hydrogen.  H|=  I.  A  gaseous  element  of  very  frequent 
occurrence  in  nature  in  a  combined  state,  especially  in  the  form 
of  water.  It  is  taken  as  the  unit  of  atomic  weights.  It  is  used 
for  the  production  of  the  lime-light. 

Hydrogen  Peroxide  (Ger.,  Wasserstoffsuperoxyd ;  Fr.,  Eau 
oxygenee  ;  Ital.,  Aequo,  ossigenatd).  H2(X  =  34.  Synonyms: 
Hydroxyl,  Hydrogen  dioxide.  Made  by  passing  carbonic  acid 
gas  through  water  in  which  barium  dioxide  (Ba02)  is  suspended. 
Barium  carbonate  is  precipitated,  hydroxyl  being  formed  in 
solution  :  BaO.,  +  CO*  +  H20  =  BaC03  +  H.,Oa.  It  is  a  powerful 
oxidiser  and  bleaching  agent,  and  is  used  to  free  prints  and 
negatives  from  the  last  traces  of  hypo,  which  it  does  by  oxidising 
it  into  sulphate ;  but  it  must  be  used  very  weak  (about  2  drms. 
to  5  ozs.),  or  the  density  of  the  negatives  and  the  tones  of  the 
prints  will  be  reduced  and  sulphur  deposited. 

Hydroquinone  (Ger.,  Hydrochinon ;  Fr.,  Hydroquinone; 
Ital.,  Idrochinone).  C6H4(OHL,)  =  no.  Synonyms:  Hydrokinone, 
Hydrochinone,  Ouinol.  It  is  prepared  commercially  by  oxidising 
aniline  sulphate  with  bichromate  of  potassium.  Solubility  :  58 
per  cent,  in  water  o°C,  10  per  cent,  in  water  at  300  ;  soluble  also 
in  alcohol,  ether,  and  glycerine.  It  is  allied  to  pyrogallol  in  che- 
mical composition,  pyro  being  a  trihydroxybenzine,  C6H4(OH)3 ; 
and  quinol,  as  |it  should  |be  called,  being  a  dihydroxy benzine. 
It  was  first  suggested  as  a  developer  by  Captain  Abney,  and 
attracted  but  little  attention  in  consequence  of  the  unsuitable  cha- 
racter of  the  accelerator, — ammonium  hydrate,  or  liq.  ammonia, 

237 


Hyd]  DICTIONARY  OF  PHOTOGRAPHY. 

— which  was  recommended  to  be  used  with  the  same,  and  also 
from  its  prohibitive  price  ;  but,  as  more  experiments  were  made 
with  it,  and  better  formulae  were  given  for  its  use,  it  crept 
gradually  into  general  favour,  and  an  enormous  reduction  in 
price  has  led  to  its  universal  adoption.  When  used  with  the 
carbonates  of  potassium  and  sodium  its  action  is  somewhat  slow, 
and  only  since  the  general  use  of  the  hydrates  of  these  alkalies 
has  it  given  satisfaction.  The  question  as  to  whether  it  is  better 
than  pyro  is  one  that  cannot  be  decided,  so  much  depending 
upon  the  personal  bias  of  the  user  of  the  same.  Many  old  opera- 
tors who  have  used  alkaline  pyro  since  its  first  introduction  still 
cling  to  it,  and  refuse  to  believe  that  quinol  is  as  good  ;  whereas 
many  others  state  that  it  is  infinitely  preferable.  For  some 
conditions  of  work  it  undoubtedly  is  far  superior  to  pyro.  The 
number  of  formulae  given  is  enormous,  almost  every  worker 
seemingly  suggesting  some  slight  modification.  The  author  has 
made  a  great  number  of  experiments,  and  believes  that  with  the 
following  formulae  good  results  can  always  be  obtained.  For 
negative  i work  : — 

No.  i. 

Quinol   154  grs.    or    10  grms. 

Sodium  sulphite  (pure  recryst.)    154  ,,  10  ,, 

Sulphurous  acid         ...       ...      17  mins.  ,,      1  c.c.m. 

Distilled  water,  to  make       ...      10  ozs.    „  250  „ 

Dissolve  the  sulphite  in  the  water  and  add  the  acid,  and  lastly 
the  quinol. 

No.  2. 

Sodium  carbonate  (pure)      ...1,300  grs.    or    84  grms. 
Potassium  hydrate  (caustic  pot- 
ash in  sticks)    154  „      „    10  „ 

Distilled  water,  to  make       ...      10  ozs.     ,,  250  c.cm. 

For  use  mix  equal  parts  of  each,  and  dilute  with  twice  or  three 
times  the  quantity  of  water.  About  4  drms.  of  each  will  be 
ample  for  a  J-plate  which  has  received  a  normal  exposure.  The 
image  should  make  its  appearance  in  about  thirty  to  forty-five 
seconds,  and  development  be  completed  in  four  or  five  minutes. 
For  under-exposure  soak  the  plate  first  in  the  accelerator  for  one 

238 


DICTIONARY  OF  PHOTOGRAPHY. 


[Hyd 


minute,  and  then  add  the  quantity  of  No.  i.  For  over-exposure 
add  I  drm.  of  a  10  per  cent,  solution  of  sodium  sulphite,  or 
5  mins.  of  bromide  of  potassium,  and  reduce  the  quantity  of 
accelerator  No.  2.  Dr.  Herklots  Vos  has  given  the  following 
formulae  as  being  all  that  can  be  desired. 

No.  i. 

Quinol   4  grs.  or  -25  grm. 

Sodium  sulphite    24   ,,    „  1*5  „ 

Distilled  water  ...    1  oz.      25  c.cm. 

No.  2. 

Potassium  bromide    60  grs.  or  4  grms. 

Distilled  water,  to  make  10  drms.  or  37  c.cm.  of  solution. 

No.  3. 

Potassium  hydrate    2  ozs.  or  60  grms. 

Distilled  water   1  oz.   ,,  25  c.cm. 

For  normal  exposure  add  5  drops  of  No.  2  and  No.  3  solutions 
to  1  oz.  of  No.  1,  and  allow  development  to  continue  for  some 
minutes  ;  then  add  another  portion  of  No.  3  to  obtain  the  required 
density.  For  under-exposure  omit  No.  2,  and  gradually  increase 
the  accelerator  No,  3  ;  for  over-exposure  increase  No.  2  to  10 
drops  to  the  ounce.  The  above  quantities  are  for  a  j-plate. 
The  following  is  recommended  by  a  well-known  firm  of  plate- 
makers: — 

No.  1. 

Quinol   160  grs.    or    10  grms. 

Sodium  sulphite         ...        ...       2  ozs.    ,,     56  ,, 

Citric  acid    60  gr.     ,,     3  8  „ 

Potassium  bromide    30  ,,      16  ,, 

Distilled  water  to    20  ozs.   ,,    500  c.cm. 

No.  2. 

Sodium  hydrate         ...        ...     160  grs.    or    10  grms. 

Distilled  water  to       ...       ...      20  ozs.     ,,  500  c.cm 

To  develop,  mix  equal  parts  of  each.  It  is  recommended  to  use 
the  alum  bath  after  development.    May  be  used  for  negative  or 

239 


Hyd] 


DICTIONARY  OF  PHOTOGRAPHY. 


positive  work.  For  positives,  whether  on  glass  or  paper,  the 
author  recommends  the  following  for  black  tones  : — 

No.  I. 

Quinol   154  grs.    or    10  grms. 

Sodium  sulphite         ...       ...  437    ,,  28  „ 

Sulphurous  acid    20  mins.  „    1*2  c.cm. 

Distilled  water  to  make        ...      10  ozs.    ,,  250  „ 

No.  2. 

Sodium  carbonate   1,300  grs.  or    84  grms. 

Potassium  hydrate     ...       ...    154  10  „ 

„       bromide    20  „  ,,    1*2  grm. 

Distilled  water  to  make        ...      10  ozs.  ,,  250  c.cm. 

Mix  in  equal  parts,  and  dilute  with  three  times  the  quantity  of 
water.  The  following  will  give  good  purplish  tones  to  trans- 
parencies on  glass,  and  brownish  tones  to  bromide  paper  : — 

Quinol   2  grs.  or    -12  grm. 

Ammonium  carbonate  ..  24  15  ,, 

bromide   ...       ...       |   „  ,,  *oi6 

Distilled  water ...       ...       ...       1  oz.         25  c.cm. 

Mix  immediately  before  using.  As  a  convenience  for  travelling, 
the  following  dry  powder  developer  will  be  found  simple  and 
convenient : — 

I. 

Quinol  90  grs.  or  6  grms. 

II. 

Sodium  sulphite  (granular)  ...       2  ozs.  60 
III. 

Carbonate  of  soda  (dried)    ...       1  oz.    „  28  „ 

Wrap  each  salt  in  waxed  paper  and  tinfoil.  Dissolve  these 
quantities  in  a  quart  of  water.  As  a  further  convenience  they 
may  be  subdivided  into  four  or  eight  packets  each,  so  as  to 
make  sufficient  quantities  for  10  or  5  ozs.  of  developer.  Although 

240 


DICTIONARY  OF  PHOTOGRAPHY.  [Hyd 

a  one-solution  developer  is  not  the  best  form,  it  may  be  found  con- 
venient for  travelling,  and  then  the  following  will  answer  well : — 

Quinol                               ...  90  grs.  or     6  grms. 

Sodium  sulphite    2  ozs.  ,,  60  ,, 

Carbonate  of  soda      ...       ...  2    ,,    ,,  60  ,, 

Distilled  water  to  make        ...  10    ,,    ,,  250  ,, 

Eosin    ...       ..        ...       ...  i^gr.    ,,  -06 

This  solution  will  keep  at  least  two  months,  and  when  required 
for  use  should  be  diluted  with  four  times  the  quantity  of  water. 
For  over-exposure  use  old  developer,  for  under-exposure  new 
developer,  and  for  normal  half  old  and  half  new.  In  using  quinol 
as  a  developer  several  precautions  are  necessary.  Absolutely 
clean  dishes  must  be  used,  as  any  trace  of  pyro  produces  a 
brown  stain.  For  negative  work  fresh  developer  should  be  used 
for  each  plate  ;  but  the  used  developer  may  be  kept  and  used 
for  bromide  paper  and  transparencies.  Both  negatives  and  posi- 
tives should  be  well  washed  after  development  prior  to  fixing  ; 
and  if  either  of  the  caustic  hydrates  of  the  alkalies  are  used,  then 
an  alum  bath  should  be  used  after  development  to  prevent  frilling. 
All  plates  and  papers  developed  by  quinol  require  clearing  and 
thoroughly  washing  after  being  fixed,  to  dissolve  out  the  slight 
precipitate  of  carbonate  of  lime  deposited  from  the  water.  Numer- 
ous researches  have  been  made  on  the  subject  of  this  reducing 
agent  and  more  numerous  still  the  formulae  that  have  been  recom- 
mended, one  of  the  most  complete  papers  was  by  Lainer,  who 
summarises  his  experiments  as  follows  : — 

A  Concentrated  Rapid  Hydroquinone  Developer. 

A.    Water   100  c. cm. 

Sodium  sulphite    2S~3°  grms. 

Hydroquinone  ...       ...       ...      10  „ 

Dissolve  these  by  the  aid  of  heat,  and  add  to  the  solution  25  grms. 
of  potassium  ferrocyanide  dissolved  in  100  c.cm.  of  water. 

B. — Dissolve  50  grms.  of  potassium  hydrate  in  100  c.cm.  of 
water,  or  30  grms.  of  sodium  hydrate  in  90  c.cm.  of  water. 

For  development,  take  60  parts  of  A,  6  to  8  parts  of  the  potash 
solution,  and  40  parts  of  water  ;  the  potash  solution  may  be 
replaced  by  10  parts  of  the  solution  of  caustic  soda.    The  two 

241  R 


DICTIONARY  OF  PHOTOGRAPHY. 


original  solutions  may  be  mixed,  and  should  then  be  diluted  with 
thrice  its  bulk  of  water. 


Other  Formulae. 


A.  Water      ...       ...       ...  600 

Hydroquinone    ...       ...  10 

Neutral  sodium  sulphite  25 

Potassium  ferrocyancide  — 

B.  Potassium  hydrate  ...  50 
Sodium  hydrate  ...  — 
Water    100 


2 

3 

4 

5 

900 

950 

1,000 

55o. 

10 

10 

10 

10 

40 

30 

35 

35 

120 

90 

25 

25 

50 

5° 

30 

60 

IOO 

90 

55o 

55o 

Developer  I. — 60  c.cm.  of  A  and  3  c.cm.  of  B,  brought  out 
a  sensitometer  image  in  three-quarters  of  a  minute  to  240 ;  but 
isiapt  to  produce  fog  with  some  kinds  of  plates.  The  addition 
of  about  12  per  cent,  of  potassium  ferrocyanide  is  found  to  have 
a  very  beneficial  effect.  Developer  2. — 60  c.cm.  of  A  and  6  c.cm. 
of  B  permits  exposures  to  be  shortened,  gives  excellent  details 
in  the  shadows,  and  allows  very  rapid  development.  Developer 
3. — 60  c.cm.  of  A  and  12  c.cm.  of  B  gives  negatives  of  a  softer 
character  than  those  given  by  Developer  2.  Developer  4  is  a 
slower  developer,  60  c.cm.  of  A  being  mixed  with  from  6  to  9  c.cm. 
of  a  50  per  cent,  solution  of  sodium  hydrate  and  diluted  with 
60  c.cm.  of  water.  Developer  5. — Equal  bulks  of  these  solutions 
are  mixed  immediately  before  use.  It  resembles  Developer  4 
in  its  action.  Acetic  acid  and  acetates  act  strongly  as  restrainers, 
yellow  prussiate  of  potash  acts  as  an  accelerator.  The  great 
fault  with  incautious  use  of  hydroquinone  is  that  one  is  very 
liable  to  obtain  negatives  with  very  great  contrasts,  and  since 
the  introduction  of  the  newer  developers  it  has  considerably 
fallen  in  use. 

Hydroxylamine  Hydrochloride  (Ger.,  Salzsdures  Hydro- 
xylamin ;  Fr.,  Chlorhydrate  d 'hydroxylamine ;  Ital.,  Chloridrato 
d'idrossilimind).  NH30HC1  ==  69-5.  Prepared  by  the  reduction 
of  nitrite  and  nitrate  of  ammonia.  It  is  very  soluble  in  water 
and  alcohol;  it  has  been  recommended  as  a  new  developing 
agent ;  but  its  price  is  at  present  decidedly  against  it,  besides 
there  being  few,  if  any,  advantages  over  hydroquinone  and  pyro- 

242 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ima 


gallol,  with  the  great  disadvantage  that  it  causes  the  film  to 
blister,  due  to  the  disengagement  of  nitrogen.  The  following  is 
the  form  recommended  by  Messrs.  Egli  &  Spiller : — 

I. 

Hydroxylamine    32  grs.  or  r8  grm. 

Citric  acid    15  „  1 

Distilled  water        ...       ...  1  oz.   ,,   25  c.cm. 

II. 

Carbonate  of  potash  ...  480  grs.  or   27  grms. 

Carbonate  of  soda   ...       ...  480  „     „    27  „ 

Distilled  water       ...       ...  10  ozs.      250  c.cm. 

Developer. 

Solution  I.    ...    30  mins.  or   2  c.cm. 

Solution  II   120    ,,           8  ,, 

Distilled  water        ...       ...  1^  oz.  37 

Sufficient  for  half-plate.  It  is  especially  recommended  for 
chloride  plates,  bromide  and  Alpha  papers. 

Hypo.    An  abbreviation  of  Hyposulphite  of  Soda  (q.v.). 

Image.  An  optical  term  denoting  the  appearance  of  any 
object  made  by  reflection  or  refraction,  and  in  this  sense  applied 
to  the  reproduction  of  an  object  upon  the  ground-glass. 

Image,  Latent.  The  action  of  light  upon  the  sensitive  salts 
of  silver  has  always  been  a  moot-point  with  scientific  photo- 
graphers, and  it  would  be  impossible  within  reasonable  limits  to 
give  all  the  arguments  pro  and  con.  For  some  considerable  time 
past,  and  even  now,  a  few  photographers  hold  that  the  action  of 
light  upon  the  sensitive  salts  is  to  set  up  a  vibratory  motion, 
which  the  developer  takes  advantage  of,  reducing  these  vibrating 
molecules  to  a  metallic  state.  This  theory,  however,  has  been 
shown,  and  it  is  generally  considered  most  conclusively  so,  by 
Captain  Abney  and  Dr.  Armstrong,  and  more  lately  by  Carey 
Lea,  of  New  York,  to  be  erroneous.  The  latter  scientist  has 
written  most  exhaustive  papers  upon  this  point,  and  has  been 
enabled  to  prepare,  chemically,  salts  identical  in  composition  and 

243 


Inc] 


DICTIONARY  OF  PHOTOGRAPHY. 


action  with  those  formed  by  the  action  of  light ;  these  he  calls 
photo-salts,  and  they  would  seem  to  be  compounds  of  a  lower 
haloid  salt,  with  the  normal  haloid  in  varying  proportions.  In 
all  cases  there  seems  to  be  an  evolution  of  the  haloid  element, 
and  the  action  has  been  thus  chemically  expressed — 

2AgBr     +     light     =     Ag2Br  +  Br. 

/  Silver  \  /     Silver     \  /Bro-\ 


It  seems  unlikely  that  all  the  molecules  of  haloid  salt  are 
reduced  ;  on  the  contrary,  but  a  very  minute  portion  is.  But,  as 
shown  in  the  article  oh  Development,  the  action  set  up  by  the 
impact  of  actinic  light  is  continued  by  the  developer.  It  has  been 
stated  that  when  the  action  of  reduction  by  light  has  once  begun, 
it  continues  indefinitely  in  the  dark ;  but  the  arguments  in  favour 
of  this  statement  are  very  weak,  as  it  has  been  shown,  on  the 
other  hand,  that  the  action  of  light  may  be  obliterated  by 
keeping. 

Confirmation  of  the  disassociation  of  the  molecule  of  bromide 
of  silver  by  light  has  been  given  by  the  researches  of  Guntz,  who 
has  been  able  to  prepare  the  sub-haloid  salts  of  silver. 

Incidence,  Angle  of.  Is  the  angle  made  by  a  ray  of  light, 
passing  through  any  point  or  line  of  a  surface,  with  the  perpen- 
dicular to  that  line  or  surface  drawn  through  the  point  in  ques- 
tion, or  to  the  tangent  of  a  circle  in  the  case  of  spherical  curves. 
The  angle  of  incidence  and  the  angle  of  reflection  are  always 
equal. 

Indian  Ink.  A  black  pigment  obtained  from  China.  It  is 
an  exceedingly  fine  lampblack,  said  to  be  produced  by  burning 
oil  of  sesame,  mixing  the  product  with  some  vegetable  gum,  and 
drying  till  it  turns  into  a  solid  cake. 

Indiaruboer  Solution.  This  is  used  for  edging  plates  or  as 
a  substratum  for  the  collodion  process,  and  also  for  mounting 
gelatino-chloride  prints.  It  may  be  dissolved  in  benzole,  chloro- 
form, or  carbon  bisulphide,  the  two  former  being  preferable  in 
the  proportion  of  ten  grains  to  the  ounce.  Pure  masticated 
rubber  should  always  be  used. 

Ink  Process.    Under  this  title  several  processes  may  be 


244 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ink 


included,  but  Lemling's  process  is  the  one  usually  meant  by  this 
term  now  ;  the  procedure  being  as  follows  : — 

Bichromate  of  potash     ...       ...         I  part. 

Distilled  water    20  parts. 

Dissolve  and  render  neutral  with  ammonia.  To  every  three 
parts  of  this  add  with  constant  stirring  in  a  mortar 

Powdered  gum-arabic    ...       ...         1  part. 

Transfer  to  a  bottle  and  shake  frequently  till  dissolved,  which 
probably  will  be  in  about  twenty-four  hours ;  it  should  then  be 
filtered  and  spread  evenly  over  a  sheet  of  albumenised  paper 
with  the  aid  of  a  Blanchard  brush.  The  paper  should  then  be 
laid,  film  up,  on  a  sheet  of  plate-glass,  a  good-sized  pool  of 
the  solution  poured  on  to  it  and  made  to  cover  it  evenly,  the 
excess  poured  off,  and  the  paper  hung  up  to  dry.  The  difficulty 
in  this  process  is  to  prevent  the  albumenised  paper  from  curling ; 
therefore  it  is  preferable  to  hold  it  paper-side  down  over  a 
jet  of  steam,  so  as  to  partially  coagulate  the  albumen  next  the 
paper,  and  then  lay  on  the  glass  ;  or  the  glass  may  be  wetted  and 
the  paper  squeegeed  to  it  with  a  rubber  roller  and  then  coated  as 
described  above.  The  operation  may  be  conducted  in  daylight 
as  the  paper  is  insensitive  whilst  wet ;  the  drying  should  be 
conducted  in  the  dark.  It  is  exposed  behind  a  negative  in  the 
usual  way,  then  laid  face  downwards  on  water  and  allowed 
to  soak  for  some  time  with  repeated  changing  of  the  water,  and 
then  it  should  be  soaked  in  alum  solution  and  again  washed.  It 
is  then  drawn  over  the  surface  of  the  following  solution  : — 

Pyrogallol  ...        ...        ...       ...        1  part. 

Distilled  water  50-80  parts. 

Or  it  may  be  floated  on  the  same  for  two  minutes,  then  thoroughly 
washed  and  floated  on  a  solution  of 

Sulphate  of  iron   ...       ...      10  parts, 

Distilled  water   100  ,, 

and  again  washed.  If  not  dark  enough  the  process  may  be  repeated. 

Another  process  sometimes  used  by  artists  and  others  for 
preparing  drawings  for  reproduction  is  as  follows.    A  print  is 

245 


Ins] 


DICTIONARY  OF  PHOTOGRAPHY. 


obtained  in  the  usual  way  either  on  albumenised,  bromide,  or 
plain  paper,  the  latter  being  preferable  ;  and  failing  this  an  image 
may  be  obtained  on  the  back  of  albumenised  paper.  As  long  as 
the  details  are  there  the  depth  of  printing  should  be  very  slight, 
no  toning  or  fixing  is  required.  The  image  is  then  traced  over 
with  Indian  ink,  with  the  aid  of  a  crowquill  or  fine  pen.  Allow 
this  image  to  dry  thoroughly  and  immerse  in 

Saturated  solution  of  iodine     ...       ...       10  parts. 

Saturated  potassium  cyanide        15  „ 

Distilled  water    ...       ...       ...       ...     500  ,, 

when  the  silver  image  will  disappear  and  the  print  may  then  be 
washed  and  dried.  The  saturated  solution  of  iodine  can  be 
prepared  by  saturating  a  10  per  cent,  aqueous  solution  of  potas- 
sium iodide. 

Insensitiveness.  When,  by  reason  of  faulty  chemicals  or 
manipulations,  the  sensitive  surface  refuses  to  record  any  action 
of  light. 

Instantaneous  Lens.  A  term  incorrectly  applied  to  lenses 
when  intended  to  convey  a  particular  construction,  as  all  types 
of  lenses  would,  in  a  sufficiently  powerful  light,  enable  in- 
stantaneous photographs  to  be  taken. 

Instantaneous  Photography  is  the  obtaining  of  negatives  by 
exposures  of  the  fractional  part  of  a  second.  The  following 
tables  and  rules  may  be  found  useful : — 

A  man  walking  3  miles  per  hour  moves       4^ft.  per  second. 

„  4  n  tt  6  m 

A  vessel  travelling  9  knots  per  hour  15  ,, 

»  12         „  „         19  » 

tt  *7  M  M  28  „ 

20        11           ft  35 

A  trotting  horse   „  39 

A  galloping  horse  ,  50  ,, 

An  express  train  at  38  miles  per  hour  „  59  ,, 

Flight  of  a  pigeon  ,,  61  „ 

Waves  during  a  storm      ...       ...  ,,  65  „ 

Express  train  at  60  miles  per  hour   ,,  88  ,, 

Flight  of  the  swiftest  birds          ...  „  264  ,, 

A  cannon  ball   „  1,625  » 

246 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ins 


An  object  moving  I  mile  per 

hour  moves 

i^ft.  per  second. 

2  miles  ,, 

1, 

3 

>i 

>> 

3 

I* 

4 

„ 

4 

11 

6 

)) 

5 

„ 

7^ 

M 

>t 

6 

11 

9 

11 

>i 

7 

„ 

IO* 

„ 

8 

11 

12 

11 

n 

9 

n 

13 

n 

M 

IO  „ 

11 

14 

1 1 

M 

ii  ii 

n 

16 

n 

II 

12  „ 

n 

I7i 

ii 

If 

13 

„ 

19 

M 

„ 

14 

11 

20^ 

11 

f| 

15 

11 

22 

11 

II 

20  ,, 

11 

29 

11 

»» 

25 

37 

11 

If 

30 

11 

44 

M 

35 

,, 

51 

ii 

40 

,, 

59 

11 

II 

45 

11 

66 

11 

II 

50 

11 

73 

,, 

II 

55 

•1 

80 

60 

,, 

88 

75 

1 10 

II 

100 

147 

11 

125 

i> 

183 

11 

II 

150 

220 

11 

To  find  the  distance  moved  by  the  image  of  an  object  on  the 
ground  glass,  multiply  the  focus  of  the  lens  in  inches  by  the 
distance  in  inches  moved  by  the  object  in  one  second,  and 
divide  the  result  by  the  distance  of  the  object  in  inches. 

Example. — Find  the  displacement  of  image  on  ground-glass 
of  an  object  moving  20  miles  an  hour,  with  a  lens  of  8£-in  locus, 
and  the  object  1 50  yds.  distant. 

8£  x  348  -5-  5,400  =  %%%  =  \  in.  per  sec.  practically. 

To  find  how  quickly  a  shutter  must  act  to  take  an  object 
247 


Ins] 


DICTIONARY  OF  PHOTOGRAPHY. 


in  motion,  that  there  may  be  a  circle  of  confusion  less  than 
i-iooth  inch  in  diameter,  divide  the  distance  of  the  object  by 
ioo  times  the  focus  of  the  lens,  and  divide  the  rapidity  of 
motion  of  object  in  inches  per  second  by  the  result,  when  you 
have  the  longest  duration  of  exposure  in  fraction  of  a  second. 
All  measurements  in  inches. 

Example. — Required  the  speed  of  a  shutter  to  take  an  object 
moving  20  miles  per  hour,  with  a  lens  of  8^-in.  focus,  the  object 
being  150  yards  distant. 

The  object  moves  29  feet  =  348  in.  per  second. 
5,400,  distance  of  object  in  inches,  ~  (8£  x  100) 
108 

=  5»4oo  ~  850  =  — 

O  J        r        ,  •  n  IO8  348      X  17 

348,  speed  of  object  per  second,  —  =  iQg — 

493 

=  —  =  55  practically. 

.*.  the  shutter  must  work  at  -fa  of  a  second. 

Knowing  the  rapidity  of  shutter  and  moving  object,  required 
to  find  the  distance  to  place  the  camera  to  give  an  image  with 
a  circle  of  confusion  less  than  T^  of  an  inch  in  diameter. 
Multiply  100  times  the  focus  of  the  lens  in  inches  by  the  space 
through  which  the  object  would  pass  during  the  exposure,  and 
the  result  is  the  nearest  distance  in  inches  between  object  and 
camera. 

Example — A  shutter  works  at  sec,  object  moves  four  miles 
an  hour;  how  near  must  camera  be  placed  with  an  8^-in. 
lens  ? 

An  object  moving  four  miles  per  hour  moves  72  in.  per 
second. 

.'.  an  object  moving  four  miles  per  hour  moves  iTV  in.  in 
■h  sec- 

17  X  IOO  X  12 

%\  X   IOO  X   I   2  X  II          =  927  m"  "~  25  y 

248 


DICTIONARY  OF  PHOTOGRAPHY.  [InS 

Dr.  Eder  gives  the  following  table  ("  Jahrbuch,"  1887): — 

Sec.  Sec.  Sec. 

Laughing  children,  etc.,  probably  require  ...     i  to  1 

Dogs  and  cats ....                                      ...     f  „  TV 

Street  scenes,  according  to  size  of  figures  ...  „  3V 

Cattle  feeding,  sheep,  etc.    ...        ...       ...    fa  „  fa 

Moving  ship  500  to  1,000  yards  off                  fa  ,,  -5V 

Moving  ship  nearer  fa  „  tU 

Animals  which  appear  on  focussing  screen  from 

one  to  two  inches  high     ...        ...        ...    fa  ,,  T-J-o 

Trotting  and  jumping  horses,  birds,  etc.   ...  T^  ,,  lifartOi^ro 

Pizzighelli  ("Anleitung  zur  Photographic"  p.  83)  gives  the 
following  useful  little  table : — 


B  * 


_B 

IS  !>> 


ti 
fl 

ti 

B 

M 
c 

£ 

Lies 

rott 

"2L 

O 

111  p 

lll|) 

ice. 

iri  O 

Horse  t 

Horse  ga 

Horse  jt 

Steams 
dista 

Train  3 
an  h 

Moving  a  distance  in  yards  per  second  of 


<u  in 


i-6  2-3 

i-8 

J8  1  57 

12 

7 

10  1 167 

Requires  an  exposure  in  seconds 


TTTT5 
-56 

■sV 

IS 
1 

TV 


US 
1 

TT5 


TffTF 
1 

S 
1 


1 

1 

5 


TUT) 

1 

"57 


TuTT 
1 

T&7T 


T0T5 


Major  Pizzighelli  wisely  adds  that  fractions  of  a  second 
smaller  than  have  not  been  introduced  into  the  above  table, 
probably  because  the  shutters  giving  shorter  exposures  than 

249 


Ins]  DICTIONARY  OF  PHOTOGRAPHY. 

this  are  not  met  with  every  day.  In  the  first  column  above, 
the  distances  of  the  object  are  expressed  as  multiples  of  the 
focal  length;  the  distance  in  yards  is  easily  reckoned  out  by 
multiplying  by  the  focus  of  lens.  Thus,  an  object  is  200 
times  the  focus  of  lens  distant,  and  using  an  8J-in.  lens, 
then  : 

8|  X  200  —  1,700  in.  =  44^  yards. 

These  distances  must  be  estimated  by  measurement  or  guess 
work.  This  latter  is  by  no  means  difficult  to  reach ;  thus 
the  following  table,  compiled  by  the  same  writer,  will  be 
of  assistance.  We  assume  that  the  mean  height  of  a  man 
is  5  ft.  9  in.  that  of  a  horse  5  ft.  3  in.,  that  when  the  height 
of  the  image  of  horse  and  a  man  appears  on  the  ground- 
glass  as  : 


Man. 

Horse. 

The  Object  is  distant  from  the  Camera. 

I|    in.  . 

in. 

50  times  the  focal  length. 

i    „  • 

3 
4 

it 

100  ,, 

It 

3 

8  11 

•  •  1 

tt 

200  „ 

It 

I 

4  »} 

i 

tt 

300 

3 

t?t  tt 

»> 

400 

1 

T  it 

500 

It 

1 

ti 

600  „ 

II 

>t 

700 

11 

3 

■3-2  }} 

3 

sir 

11 

800 

TS  tt 

1 

TT> 

n 

900  „ 

i 

15  ft 

1 

ITS 

tt 

1,000  ,, 

II 

For  the  sake  of  convenience,  I  have  carried  this  table  the  reverse 
way,  that  is  to  say,  giving  the  distances  of  the  above-named 
object  as  less  when  the  height  of  the  image  of  a  man  and  horse 
is  respectively  greater. 

Man. 
If  in. 

o  5 

tt 

2-7- 

''s  n 

3tV  tt 

31-  M 

4t\  1, 

5  H 


Horse. 

■  I,1 

■  2TV 

•  2| 

■  3iV 

•  3h 

■  31 

•  4i 


The  Object  is  distant  from  the  Camera. 
40  times  the  focal  length. 
30 
24 
20 
18 
16 
14 

250 


DICTIONARY  OF  PHOTOGRAPHY.        •  [Ins 


Another  table  compiled  by  MM.  Henry  Hermagis  and  Rossignol 
is  also  convenient : — 


Approx* 

Approx. 

Distance 

Subject. 

speed  of 

Approx. 

height  of 

in  yards. 

shutter 

Reduction. 

man 

in  seconds. 

in  inches. 

-■»  X 

3? 

otandmg  children  or 

1 

1 

1  0 

half-length  men  with 
heads  about  \  inch 
from  top  to  chin 

7h 

See-saw,  skipping  chil- 
dren, etc.* 

&  to  ffV 

ri 

2\  to  2f 

12  to  l6\ 

Horse   walking,  dan- 
cers "j" 

A  to  CV 

4  to  l£ 

12  to  24 

Acrobats,  clowns,  dan- 

1 <-<-»  1 

tJTT  tO  XI7Ij 

¥7  to  -j^ 

i  to  I§ 

cers,  etc.f 
Moving     people,  but 

15  to  20 

rfr  to  CV 

tO  7Tr 

1  to  I| 

not  walking  about — 
crowds,  bathers 

i8£  to  30 

People   walking,  sol- 

ft ^  tJo 

}  to  t\ 

diers  quick-march- 
ingf 

22  to  32 

People,  troops,  yachts, 

1 

TT>0 

*  to  f 

tramcars  % 

27 

Horse     trotting,  in- 

TV tO  A 

1 

115 

i 

fantry  charging,  run- 

ners | 

33 

Calm  sea,  ships,  at  rest 
or  moving  + 

1 

1^0 

1 
2 

43 

1 

f>7> 

1 

1TH7 

I 

50 

 1 

T7tf 

en 

j  J 

Train   (35    miles  per 
hour),  tricycle, 
sledge  f 

ii'&TF 

1 

4 

70  to  75 

Express  train,  balloon, 
storm   waves,  grey- 
hound coursing, 
skater,,  racehorse, 
dynamite  explosion 

71 

i 

The  exposure  to  be  made  at  the  moment  of  partial  rest  or  least  movement, 
t  Object  moving  across  the  field  of  view. 
I  Object  moving  across  the  plate. 

§  Object  moving  to  or  from  lens  or  only  slightly  across. 


The  secret  of  successful  results  with  instantaneous  work  is  to 
watch  the  moving  object  till  it  attains  that  position  which  the 

251 


Ins] 


DICTIONARY  OF  PHOTOGRAPHY. 


French  call  le  point  morty  and  which  is  well  seen  in  the  case  of  a 
ball  thrown  perpendicularly  up  into  the  air.  For  some  time  the 
ball  travels  up,  and  then  just  for  one  almost  inappreciable  period 
of  time  it  is  stationary,  and  begins  its  downward  course,  and  an 
exposure  should  be  made  just  at  the  moment  of  reversal  of 
motion.  It  will  be  found  that  with  nearly  every  moving  object 
some  such  point  mort  will  occur,  and  the  successful  worker  seizes 
this  moment  to  fire  off.  Too  many  amateurs  allow  their  very 
laudable  ambition  to  run  away  with  their  sense,  and  expect  the 
combination  of  shutter,  lens,  and  plate  to  do  impossibilities.  For 
very  quick  work,  brilliant  sunshine  is  absolutely  necessary,  and 
two  important  points  should  be  taken  into  consideration — (i) 
That  the  nearer  a  moving  object  is,  the  more  rapid  must  be  the 
action  of  what  is  called  the  shutter,  which,  by  way  of  parenthesis, 
might  with  equal  force  be  termed  an  opener  ;  (2)  The  longer  the 
focus  of  the  lens,  the  quicker  the  shutter  should  act.  Another 
point  is  that  when  an  object  is  moving  across  the  field  of  view,  or 
more  or  less  obliquely  to  the  axis  of  the  lens,  the  shutter  must  act 
more  quickly,  whilst  with  an  object  moving  parallel  to  the  axis  of 
the  lens,  or  away  from  or  towards  the  lens,  the  displacement  on 
the  ground  glass  or  the  difference  between  the  size  of  the  image 
at  two  points  is  by  no  means  so  great  as  in  the  first  case  ;  and  to 
improve  matters  the  theoretical  impossibility,  the  depth  of  focus 
of  the  lens,  is  again  of  assistance.  Many  commercial  shutters  are 
fitted  with  an  index  showing  the  speed  given  by  the  shutter  when 
certain  levers,  etc.,  are  placed  in  certain  positions,  but  strict 
reliance  cannot  always  be  placed  upon  such  speeds.  Methods 
of  testing  instantaneous  shutters  will  be  treated  of  under  that 
heading. 

Instantaneous  Shutters.   See  Shutters. 

Intensification  means  the  increasing  of  the  deposit  or  the 
printing  density  of  a  negative.  There  are  several  methods  of 
doing  this;  but  the  majority  consists  in  the  use  of  mercuric 
chloride,  and  then  subsequent  darkening.  Before  intensifying  a 
negative  with  mercury  it  is  absolutely  essential  that  it  should  be 
absolutely  free  from  hyposulphite  of  soda.  It  is,  therefore, 
advisable  to  give  the  negative  a  thorough  washing,  and  then 
immerse  for  10  mins.  in  a  5  per  cent,  solution  of  hydrogen 
peroxide,  and  again  wash.    Negatives  which  have  been  allowed 

252 


DICTIONARY  OF  PHOTOGRAPHY. 


[Int 


to  dry  should  be  well  soaked  in  water  before  being  bleached,  and 
varnished  negatives  must  of  course  have  the  varnish  removed  by 
means  of  methylated  spirit,  and  then  soaked.  The  mercuric 
solution  is  prepared  as  follows  : — 

Perchloride  of  mercury      ...       ...       ...       2  parts. 

Hydrochloric  acid   I  part. 

Water    100  parts. 

The  hydrochloric  acid  should  be  placed  on  the  powdered  mercuric 
chloride,  and  then  the  water  added.  The  negative  to  be  in- 
tensified, having  been  previously  treated  as  above  suggested, 
should  be  laid  in  the  solution,  and  the  dish  gently  rocked  till  on 
looking  at  the  back  of  the  plate  it  is  seen  to  be  quite  white.  It 
should  then  be  thoroughly  washed  for  at  least  20  minutes  in 
running  water,  and  then  immersed  in  one  of  the  following 
solutions  : — 

I. 

Sodium  sulphite      ...       ...       ...       ..,       1  part. 

Water      6  parts. 

II. 

The  ordinary  ferrous  oxalate  developer. 
III. 

Hydroquinone  developer. 
IV. 

Liquid  ammonia  fort.    1  part. 

Water    10  parts. 

V. 

Silver  nitrate  ...       ...       ...       ...      20  parts. 

Distilled  water    ...    500  „ 

and  add  gradually 

Potassium  cyanide   20  parts. 

Distilled  water       ...       ...       ...       ...  500 

Shake  well  after  each  addition,  till  only  a  small  quantity  of 
white  flocculent  precipitate  remains.  It  is  important  that  the 
solution  should  never  be  quite  free  from  sediment. 

253 


Int] 


DICTIONARY  OF  PHOTOGRAPHY. 


VI. 


Potassium  cyanide  ... 
iodide 


i\  parts. 

2\  „ 


Mercuric  chloride 
Distilled  water 


iooo 


VII. 


Schlippe's  salt 


10  parts. 


Distilled  water   400 

Ammonia     ...       ...       ...       ...       ...       5  „ 

The  ordinary  method  of  intensifying  is  to  adhere  to  the  use  of 
one  solution  as  a  blackening  agent ;  but  it  frequently  happens 
that  the  same  degree  of  increment  is  neither  desirable  nor 
necessary,  then  choice  may  be  made  from  the  above  solutions. 
Mr.  Chapman  Jones  has  tabulated  in  convenient  form  the  action 
of  many  of  these.  He  says  : — "  In  the  following  series  of  opera- 
tions each  change  is  supposed  to  be  thorough — that  is,  that  the 
change  of  colour  in  every  case  shall  be  visible  clearly  at  the  back 
of  the  plate  in  the  densest  part  of  the  negative.  (1)  Mercuric 
chloride,  followed,  after  well  rinsing,  with  sodium  sulphite,  gives 
the  little  addition  of  brilliancy  sometimes  wanted  in  a  carefully 
made  and  successful  negative ;  (2)  mercuric  chloride  on  the 
original  negatives,  followed,  after  thorough  washing,  by  ferrous 
oxalate,  gives  about  as  much  increase  of  density,  as  compared 
with  No.  I.,  as  No.  I.  gives  when  compared  with  the  original 
negative ;  (3)  a  repetition  of  the  application  of  mercuric  chloride 
and  ferrous  oxalate — that  is,  these  re-agents  applied  to  the  result 
of  No.  II. — gives  another  step  in  the  intensification ;  *  (4)  the 
result  of  No.  III.  may  be  treated  again  with  mercuric  chloride 
and  ferrous  oxalate,  and  so  on,  as  may  be  necessary ;  (5)  the 
fourth  or  fifth  consecutive  application  of  mercuric  chloride  and 
ferrous  oxalate  will  probably  give  a  result  equal  to  that  of  the 
uranium  intensifier  acting  upon  the  original  negative ;  (6)  if  a 
still  greater  effect  is  desired,  the  lead  intensifier  may  be  used  on 
the  original  negative."  Continuing  this  series  we  may  say  that 
the  action  of  No.  V.  is  fully  equal  to,  if  not  slightly  greater  than, 
mercuric  chloride,  followed  by  ammonia;  whilst  No.  VI.  gives 

*  The  result  of  this  treatment  is  about  equal  to  the  action  of  mercuric 
chloride,  followed  by  ammonia,  upon  the  original  negative. 


254 


DICTIONARY  OF  PHOTOGRAPHY. 


[Int 


as  great  increase  as  the  lead  intensifler  if  desired.  No.  VII. 
about  the  same  as  No.  V.  Instead  of  hydrochloric  acid  in  the 
bleaching  or  mercuric  chloride  solution,  many  recommend  potas- 
sium bromide  or  ammonium  chloride  ;  either  may  be  used,  with- 
out any  difference  in  results  being  detected.  Nos.  II.  and  III. 
solutions  give  about  the  same  density  ;  Nos.  V.,  VI.,  and  VII.  are 
all  poisonous,  as  is  also  the  mercuric  chloride  solution.  The 
bleached  negative  should  not  be  allowed  to  remain  too  long  in 
No.  V.,  or  else  the  shadows  are  attacked.  When  the  negative 
is  placed  in  No.  VI.  it  turns  first  bright  yellow,  then  much  darker 
brown.  At  this  stage  it  is  very  dense,  and  only  extremely  thin 
negatives  should  be  removed  now  ;  for  normal  work,  the  negative 
should  be  left  in  still  longer  till  it  turns  a  lighter  brown.  No.  VII. 
gives  a  bright  reddish-brown  negative.  Whichever  darkening 
solution  is  used,  it  should  be  allowed  to  act  till  the  back  of  the 
image,  as  seen  through  the  glass,  is  dark,  and  then  thoroughly 
washed. 

The  Uranium  Intensifler.  This  stains  the  image  a  bright 
reddish-brown.  It  is  absolutely  necessary  that  all  hypo  should 
be  eliminated 

Potassium  ferridcyanide   I  part. 

Uranium  nitrate                          ...       ...  I  ,, 

Acetic  acid,  glacial   10  parts. 

Water                             ...       ...       ...  100  ,, 

The  plate,  after  intensification,  should  be  well  rinsed  and  dried  ; 
continuous  washing,  especially  in  ordinary  tap  water,  removes 
the  intensification  bodily.  This  very  defect  makes  this  process 
useful,  as  by  means  of  an  alkali  any  part  of  a  negative  intensified 
with  uranium  can  be  bleached  by  treatment  with  ammonium 
carbonate. 

The  Lead  Intensijier.  This  gives  a  very  dense  increment,  and 
is,  therefore,  rarely  necessary  or  used. 

Potassium  ferridcyanide    ...    6  parts. 

Lead  nitrate ...       ...       ...       ...       ...  4 

Acetic  acid,  glacial  ...    10  ,, 

Distilled  water                           ...       ...  100  ,, 

Soak  the  negative  in  this  solution  till  bleached,  then  wash 
thoroughly,  and  flood  with 

255 


Int]  DICTIONARY  OF  PHOTOGRAPHY. 

Nitric  acid    ...       ...       ...       ...       ...       1  part. 

Water    7  „ 

Rinse  well,  and  pour  over  it  ammonium  sulphohydrate  ;  then 
wash  well  and  dry. 

Silver  Intensifiers.  Whilst  some  operators  still  hold  to  this, 
the  relic  of  old  wet- plate  days,  it  has  not  found  its  way  into 
general  practice.  It  is  difficult  to  avoid  the  occurrence  of  stains, 
as  silver  nitrate  so  readily  combines  with  gelatine.  Several 
formulae  have  been  suggested. 

A. 

Pyrogallol    1  part. 

Citric  acid    ...       ...       ...       ...       ...       2  parts. 

Distilled  water   300 

B. 

Silver  nitrate    2  parts. 

Distilled  water       ...       ...       ...       ...    100  „ 

The  plate  should,  first  of  all,  be  flowed  over  once  or  twice  with 
Solution  A,  and  then  to  every  50  parts  of  A  30  to  40  parts  of  B 
should  be  added.    Belitzski  suggests  the  following : — 

A. 

Gallic  acid   1  part. 

Hot  distilled  water   100  parts. 

Dissolve  and  filter  ;  when  cold,  add  an  equal  volume  of 

Silver  nitrate         ...       ...       ...       ...       1  part. 

Acetic  acid,  glacial   1  „ 

Distilled  water    50  parts. 

The  following  has  also  been  suggested  : — 

I. 

Silver  nitrate  ...       ...       ...       ...      22  parts. 

Distilled  water    ...        ..    250  „ 

II. 

Potassium  bromide  ...       ...       ...       ...      10  parts. 

Distilled  water       ...       ...       ...       ...     25  ,, 

256 


DICTIONARY  OF  PHOTOGRAPHY. 


[Iro 


Mix,  collect  the  precipitate,  wash  thoroughly,  and  dissolve  in 

Sodium  hyposulphite        ...       ...       ...      60  parts. 

Distilled  water    170  ,, 

The  mixture  is  thoroughly  stirred,  allowed  to  stand  for  a  few 
hours,  and  filtered,  sufficient  water  being  added  to  make  the 
total  bulk  measure  450  parts.  The  plate  is  soaked  in  this 
solution  for  5  minutes,  drained,  and  a  ferrous  oxalate  developer 
applied,  and  then  washed  and  dried.  The  following  intensifier 
has  also  been  suggested  for  negatives  of  line  work,  but  is  also 
applicable  to  ordinary  work  : — 

A. 

Potassium  bromide   1  part. 

Water    16  parts. 

B. 

Copper  sulphate     ...    1  part. 

Water    16  parts. 

Mix  in  equal  proportions,  and  flow  over  the  plate  till  the  image 
is  bleached,  then  wash  well,  and  blacken  with 

Silver  nitrate    1  part. 

Water    16  parts. 

or 

Ammonium  hyposulphite  ...       ...       ...       1  part. 

Water    4  parts. 

Then  wash  and  dry. 

Iodine  (Ger.,  lod;  Fr.,  lode ;  Ital.,  Iodid).  I  =  127.  One  of 
the  halogen  elements.  Is  obtained  from  seaweed,  and  appears 
commercially  in  metallic  bluish-grey  scales.  Solubility :  1  in 
7,000  of  water,  1  in  12  of  alcohol,  1  in  4  of  ether ;  very  soluble  in 
a  solution  of  any  alkaline  iodide.  Thirty  grains  of  iodine  and 
30  grs.  of  potassium  iodide  will  dissolve  in  one  drm.  of  distilled 
water.  The  metalloid  itself  is  of  little  use,  but  when  in  combi- 
nation as  iodide  is  much  used  for  emulsions,  etc. 

Iridescent  Stain.   See  Fog. 

Iron,  Ammonio-Citrate  of  (Ger.,  Citroncnsaurcs  Eisenoxy- 
dammon  ;  Fr.,  Ammonio-citrate  de  fer,  Citrate  ammoniacal  dc 

257  S 


Iro] 


DICTIONARY  OF  PHOTOGRAPHY. 


fer;  Ital.,  Citrato  diferro  ammoniacale).  Fe2(NH4)2  (C6H507)3. 
Synonym :  Ferric  Ammonium  Citrate  =  293.  Is  prepared  by 
dissolving  ferric  hydrate  in  citric  acid,  and  adding  liq.  ammonia 
till  neutral.  It  should  be  in  small  transparent  scales  of  a  deep 
reddish-brown  colour,  and  peculiar  mousey  odour.  Solubility  : 
1  in  0-5  parts  of  water  ;  almost  entirely  soluble  in  alcohol. 
Five  parts  dissolved  in  7*5  parts  of  water  make  10  parts  of  solu- 
tion. It  is  used  in  the  ferro-prussiate  process.  Should  be  kept 
in  the  dark. 

Iron,  Ammonio-Oxalate  of  (Ger.,  Oxalsaures  Eisenoxydul- 
ammoniak;  Fr.,  Oxalate  ammoniaco-ferrique ;  Ital.,  Ossalato 
di  ferro  ammoniacale?)  Fe2(NH4)2(C204)4  =  360.  Synonym  : 
Ferrous  Ammonium  Oxalate.  Prepared  by  dissolving  ferric 
hydrate  in  oxalic  acid  and  adding  ammonium  oxalate.  It  occurs 
in  brilliant  emerald  crystals,  which  should  be  kept  in  the  dark, 
as  they  are  partially  reduced  by  light  to  a  ferrous  state.  Ninety 
parts  are  soluble  in  100  parts  of  cold  water,  and  126  parts  in 
100  of  boiling  water.  Used  in  platinotype  and  blue-printing 
processes. 

Iron,  Ammonio-Sulphate  of  (Ger.,  Schwefelsaures  Eisen- 
oxydtdammon ;  Fr.,  Sulfate  ferreux  ammoniacal ;  Ital.,  Solfato 
di  protossido  diferro  e  d'ammoniaca).  Fe(NH4)22S046H20  = 
392.  A  double  salt  of  iron  and  ammonium,  proposed  as  a  sub- 
stitute for  ferrous  sulphate ;  but  its  action  is  much  feebler, 
though  the  salt  and  its  solution  are  more  stable.  One  ounce  of 
ferrous  sulphate  is  equal  to  1^  ozs  of  the  double  salt.  The 
author  has  found  it,  however,  a  good  but  slow  developer  for 
bromide  papers.  Solubility  :  .about  1  in  6  of  cold  water  ;  liable 
to  decompose  in  hot  water ;  insoluble  in  alcohol.  Was  fre- 
quently used  for  developing  wet  collodion  plates. 

Iron,  Oxalate  (Ger.,  Oxalsaures  Eisenoxyd,  Ferridoxalat ; 
Fr.,  Oxalate  ferrique;  Ital.,  Ossalato  di  perossido  di  ferro). 
Fe2(C204)3.  An  olive-brown  syrupy  liquid,  which  cannot  be 
crystallised,  except  with  great  difficulty.  It  is  prepared  by  dis- 
solving ferric  hydrate  in  oxalic  acid.  A  more  convenient  method 
is  to  dissolve  556  grs.  of  ferrous  sulphate  in  1  oz.  of  distilled  water, 
to  which  \  drm.  of  strong  sulphuric  acid  has  been  added,  and  to 
add  nitric  acid,  in  small  quantities  at  a  time,  keeping  the  whole 

258 


DICTIONARY  OF  PHOTOGRAPHY. 


[Iro 


boiling  till  ferric  sulphate  is  formed,  which  can  be  recognised  by 
the  solution  not  giving  a  blue  precipitate,  with  potassium  ferro- 
cyanide.  Now  add  ammonia  till  no  further  precipitate  is  formed, 
collect  and  wash  the  precipitate,  and  mix  it  with  a  cold  solution 
of  378  grs.  of  oxalic  acid  in  4  ozs.  of  distilled  water,  and  allow  it 
to  stand  in  the  dark  for  some  days.  The  resulting  solution  con- 
tains 376  grs.  of  ferric  oxalate.  It  may  also  be  made  by  dis- 
solving 10  parts  of  ferric  chloride  in  10  parts  of  water,  and  adding 
4  parts  of  solid  oxalic  acid  and  1  part  of  water,  and  allowing  to 
stand  in  the  dark  for  some  days.  The  resulting  solution  will 
contain  119  parts  of  ferric  oxalate.  The  solution  used  in  platino- 
type-printing  should  contain  100  grs.  of  ferric  oxalate  per  ounce ; 
therefore  the  above  solutions  must  be  diluted  till  of  that 
strength. 

Iron,  Oxalate  of  (Ger.,  Eisenoxalat ;  Fr.,  Oxalate  ferreux ; 
Ital.,  Ossalato ferrico).  FeC2042H20=i90.  Synonym:  Ferrous 
Oxalate.  Prepared  by  decomposition  of  sulphate  of  iron  and 
oxalic  acid.  It  is  but  rarely  used  dry,  being  generally  prepared 
as  wanted  in  solution  by  double  decomposition  by  adding 
solution  of  sulphate  of  iron  to  solution  of  oxalate  of  potash. 
(See  Developer.)  It  is  sparingly  soluble  in  water,  more 
soluble  in  any  solution  of  alkaline  oxalate.  It  is  the  develop- 
ing agent  of  the  ferrous-oxalate  developer,  which  has  rather 
more  adherents  on  the  Continent  than  in  England. 

Iron,  Per  chloride  of  (Ger.,  Ferrichlorid,  Eisenchlorid ;  Fr., 
Perchlorure  de  fer,  Chlorure  ferrique;  Ital.,  Clornro  ferrico). 
Fe2Cl6,6H20=433.  Synonym:  Ferric  Chloride.  Prepared  by 
passing  chlorine  over  red-hot  iron  filings,  when  the  ferric 
chloride  distils  over.  It  can  also  be  made  by  dissolving  iron 
wire  in  hydrochloric  acid,  adding  nitric  acid,  and  heating  till  the 
ferrous  chloride  first  formed  is  converted  into  ferric.  It  occurs 
in  yellowish-red  opaque  masses,  which  are  very  deliquescent. 
Solubility:  160  per  cent  in  cold  water;  soluble  also  in  alcohol 
and  ether.  It  is  used  for  the  reduction  of  negatives,  for  cyano- 
type  paper,  for  etching  copper  and  zinc. 

Iron,  Sulphate  of  (Ger.,  Eisenvitriol,  Schwefelsaures 
Eisenoxydul ;  Fr.,  Sulfate  ferreux ;  Ital.,  Solfato  di  ferro). 
FeS047H20  =  278.    Synonyms:  Ferrous  Sulphate,  Protosulphate 

259 


Isi] 


DICTIONARY  OF  PHOTOGRAPHY. 


of  Iron,  Copperas,  Green  Vitriol.  Prepared  by  dissolving  iron 
wire  in  dilute  sulphuric  acid,  evaporating  and  crystallising.  The 
crystals  should  be  of  a  fine  bluish-green  colour,  free  from  any 
adherent  brownish  rusty  powder,  which  is  caused  by  the  action 
of  the  oxygen  of  the  air,  the  product  being  an  oxy-sulphate :  to 
this  action  is  also  due  the  deteriorations  of  solutions  of  this  salt. 
When  this  change  in  colour  of  a  solution  is  noticed,  it  should  be 
rejected  and  fresh  solution  used.  The  solution  may  be  preserved 
for  some  time  by  the  addition  of  a  crystal  of  sulphate  of  copper 
whilst  fresh.  Solubility:  I  in  1*5  of  water;  insoluble  in  alcohol 
and  ether. 

Isinglass.  The  purest  form  of  gelatine  known,  obtained 
from  the  swimming  bladder  or  sound  of  the  sturgeon.  The 
finest  is  exported  from  Russia. 

Isochromatic,  Orthochromatic,  or  Orthoskiagraph^ 
Photography.  These  terms  are  used  to  distinguish  that  branch  of 
photography  which  attempts  to  render  in  correct  or  more  truthful 
gradations  the  colours  as  seen  by  the  human  eye.  The  two 
words  "  iso-"  and  "  ortho-chromatic  "  are  derived  from  Greek  roots 
signifying  equal  or  correct  colour  tones  ;  and  whilst  neither  are 
scientifically  accurate  in  their  description,  as  they  are  in  common 
use,  they  are  here  used.  The  merest  tyro  is  too  soon  aware  that 
the  sensitive  salts  of  silver  are  incapable  of  translating  colours 
into  correct  monochrome  as  seen  by  the  human  eye.  Thus  a 
Dright  yellow  sunflower  or  skein  of  yellow  wool  is  reproduced  by 
photography  as  black,  and  many  shades  of  blue  are,  though 
visually  dark  reproduced  as  nearly  white.  In  the  article  upon 
the  Spectrum  (g.v.)  it  will  be  seen  that  a  ray  of  white  light  is 
split  up  into  its  various  constituent  rays  of  different  colours  :  the 
brightest  of  these  colours  to  the  human  eye  is  yellow,  and  then 
orange,  two  colours  which  are  reproduced  by  black.  As  the 
question  of  colour  is  so  closely  connected  with  this  subject,  a 
brief  consideration  of  colour  will  not  be  out  of  place.  No  sub- 
stance known  possesses  any  colour  of  itself.  Colour  is  caused 
solely  by  the  action  of  the  substance  on  the  light  which  falls  upon 
it.  Natural  bodies  possess  the  power  of  absorbing  the  light  which 
enters  them,  and  they  have  this  power  in  a  selective  manner; 
that  is,  some  objects  select  and  absorb  certain  of  the  coloured 
rays  and  reflect  others.    When  all  the  light  is  wholly  absorbed, 

260 


DICTIONARY  OF  PHOTOGRAPHY.  [ISO 

the  substance  appears  black ;  but  when  all  the  rays  of  light  are 
equally  but  not  entirely  absorbed,  grey  is  the  resultant  tint. 
Colour,  therefore,  is  due  to  the  absorption  or  extinction  of 
certain  of  the  coloured  rays  of  white  light  within  the  object,  and 
the  remaining  rays  are  reflected  to  the  eye,  imparting  to  that 
object  its  characteristic  colour.  It  must,  however,  be  borne  in 
mind,  that  all  objects,  irrespective  of  colour,  reflect  white  light 
when  illuminated  by  white  light.  An  engraver,  when  translating 
into  monochrome  any  coloured  objects,  gives  not  only  a  correct 
form,  but  also  a  correct  idea  of  colour,  by  giving  varying  depths 
of  deposit  of  the  pigment  used,  so  as  to  give  to  the  eye,  were  a 
gamut  of  colours  engraved,  a  steadily  increasing  depth  of  tint 
from  absolute  white  to  deepest  black,  so  that  each  tint  or  colour 
receives  its  quantum  of  deposit  that  will  accord  to  some  extent 
at  least  with  the  colours  as  they  affect  the  human  eye.  In 
the  diagram  on  next  page,  fig.  43,  are  shown  what  are  called  the 
primary  colours  of  the  spectrum,  traversed  by  numerous  dark 
lines,  which  are  called  Fraunhofer's  lines,  after  their  discoverer. 
To  give  an  idea  of  the  relative  luminosity  of  colours  to  the 
human  eye,  the  following  diagram  has  been  prepared,  from 
which  it  will  be  seen  that  the  greatest  luminosity  is  between  D 
and  E  fig.  44,  or  in  the  yellow,  shading  off  rapidly  through  orange 
on  one  side  to  the  red,  and  through  yellowish-green  and  green  to 
the  violet  on  the  other.  In  fig.  45  is  given  the  curve  showing 
the  luminosity  of  colours  to  the  ordinary  photographic  dry  plate. 
Thus  it  will  be  seen  that  the  most  luminous  part  to  the  dry  plate 
or  photographic  retina  is  between  F  and  H,  and  practically  no 
luminosity  between  C  and  F,  where  the  greatest  visual  luminosity 
resides.  It  is  obvious,  therefore,  that  to  reproduce  colours  in  correct 
gradation  as  seen  by  the  human  eye,  we  must  in  some  way  exalt 
the  sensitiveness  of  the  ordinary  plate  to  green,  yellow,  orange, 
and  orange  red,  and  at  the  same  time  reduce  the  sensitiveness  to 
blue.  It  has  been  found  that  the  particles  of  silver  haloid  are 
most  sensitive  to  those  colours  which  they  absorb,  and  numerous 
experiments  have  been  undertaken  to  find  a  substance  which 
would  enable  the  silver  sal  to  absorb  the  whole  of  the  rays  in  the 
same  intensity  as  we  see  them  ;  but  this  has  been  found  so  fai 
impossible,  and  although  means  have  been  discovered  to  rendei 
the  silver  salts  more  sensitive  to  the  less  refrangible  rays  between 
C  and  F,  which  are  most  luminous  to  the  eye,  yet  they  still 

261 


DICTIONARY  OF  PHOTOGRAPHY. 


[ISO 


remain  most  sensitive  to  the  blue  rays  about  G.  These  colours 
are  toned  down  or  robbed  of  some  of  their  actinic  value  by  being 
filtered  through  coloured  media;  but  unfortunately  the  total 
sensitiveness  of  the  whole  plate  is  lowered  in  consequence. 
Colonel  Waterhouse  was  the  first  to  suggest  the  application  of 


NMLH        C  PEDCBA 


Kig.  46. 


eosin,  one  of  the  coal-tar  dyes.  Numerous  other  experimental- 
ists, such  as  Abney,  Carey  Lea,  Eder,  Vogel,  and  Bothamley, 
continued  the  researches  in  this  direction.  I  do  not  consider  it 
necessary  to  enter  at  great  length  into  the  chemical  composition 
the  various  dyes  used.  Nor  shall  I  refer  to  any  extent  to  the 
chemical  theories  involved  in  this  question.  For  information  on 
this  point  the  reader  is  referred  to  Professor  Meldola's  interest- 

263 


ISO]  DICTIONARY  OF  PHOTOGRAPHY. 

ing  work  on  "  The  Chemistry  of  Photography  "  (p.  288,  et.  seq.). 
Vogel  was  the  first  to  formulate  a  workable  process  for  using 
these  dyes  in  1873,  but  his  researches  were  confined  to  the 
collodion  process  only.  In  1882,  Attout  Tailfer,  a  French  chemist, 
successfully  worked  a  process  for  the  gelatine  dry  plates,  and 
this  process  is  protected  by  a  patent  in  England  and  France,  and 
it  is  worked  commercially  by  Messrs.  B.  J.  Edwards  and  Co. 
Tailfer's  process  consists  of  the  use  of  eosin  or  erythrosin  in 
conjunction  with  ammonia,  and  the  same  may  be  added  to  the 
emulsion  at  the  moment  of  formation  of  the  sensitive  salt,  or  the 
previously  prepared  and  coated  plate  may  be  bathed  in  such  a 
solution  ;  and  these  plates  are  thereby  rendered  more  sensitive 
to  yellow  and  yellowish-green.  Dr.  Vogel  has  introduced  com- 
mercially a  process  in  which  u  azaline  "  is  used,  and  this  is  said 
to  be  a  mixture  of  quinoline  blue  (cyanin)  and  quinoline  red,  by 
means  of  which  the  sensitiveness  is  still  further  increased  for  the 
orange,  orange-red,  and  red  rays.  The  chart  of  curves  on  p.  136 
is  taken  from  Meldola's  work  mentioned  above,  and  is  constructed 
from  results  given  by  Bothamley  and  Abney,  and  it  shows  the 
relative  sensitiveness  of  the  film  dyed  with  various  colouring 
matters.  (1)  Violet  dyes  ;  (2)  green  dyes  ;  (3)  iodine  green  ;  (4) 
cyanin;  (5)  eosin;  (6)  ammoniacal  rose,  Bengal;  (7)  coerulein  ; 
(8)  chrysaniline  ;  (9)  eosin  on  chloride  of  silver ;  (10)  eosin  and 
cyanin  mixed;  (11)  erythrosin  on  iodide  of  silver  and  nitrate  of 
silver;  (12)  erythrosin  on  bromide  of  silver;  (15)  erythrosin  on 
chloride  of  silver  ;  (14)  cyanin  on  chloride  of  silver.  Where  the 
haloid  is  not  specified  bromide  of  silver  has  been  used.  It  will 
be  seen  by  an  examination  of  the  above  chart  that,  although  the 
sensitiveness  of  the  haloid  salts  is  increased  towards  the  less 
refrangible  rays  beyond  E  in  the  yellow  and  red,  yet  the 
greatest  sensitiveness  is  still  in  G  and  H  in  the  blue  ;  therefore, 
to  obviate  this,  a  coloured  screen  is  used,  usually  of  glass  of  a 
more  or  less  deep  tint  of  yellow,  which  was  first  suggested  by 
Professor  Crookes  when  editor  of  the  Photographic  News,  long 
before  any  iso-  or  ortho-chromatic  process  was  thought  of.  The 
glass  screens  may  be  used  either  in  front  of  the  lens,  between 
the  combinations  of  a  doublet,  or  behind  the  lens  ;  and  it  should 
be  of  absolutely  plain  glass,  with  parallel  surfaces,  so  as  not  to 
interfere  with  the  definition  of  the  lens ;  or  a  really  serviceable 
makeshift  may  be  made  according  to  the  plan  proposed  by 

264 


DICTIONARY  OF  PHOTOGRAPHY. 


[ISO 


Engler,  in  which  glass  plates  are  first  of  all  waxed,  and  then 
polished  and  coated  with  a  plain  collodion,  as  free  from  structure 
as  possible,  and  when  thoroughly  dry  are  coated  with  gelatine, 
stained  to  the  desired  tint  with  aurantia  or  Manchester  yellow. 
For  general  use  a  good  lemon  tint  should  be  made.  When 
thoroughly  dry  the  gelatine  film  may  be  stripped  from  the  glass 
and  cut  into  pieces,  and  enclosed  between  small  brass  plates  or 
cardboard,  cut  in  the  form  of  the  ordinary  diaphragm,  in  place  of 
which  it  is  used.  In  working  iso-  or  ortho-chromatic  plates 
extreme  caution  should  be  exercised  as  to  the  illumination  of  the 
dark-room  ;  as  little  light  as  possible,  and  that  of  only  a  deep 
ruby,  should  be  used,  and  the  plate  should  be  covered  as  far  as 
possible  during  development.  No  special  developers  are  required 
as  the  plates  will  work  with  any  ordinary  developer,  whether 
pyro,  quinol,  or  ferrous  oxalate.  Their  sensitiveness  to  white 
light  is  generally  about  the  same  as  other  plates,  and  when  used 
with  a  yellow  screen  require  from  three  to  ten  times  the  ordinary 
exposures,  according  to  the  depth  of  tint.  The  value  of  colour- 
sensitive  plates  is  seen  in  the  better  rendering  of  foliage,  distance 
clouds,  and  water,  and  in  portraiture  in  the  suppression  to  a  great 
extent  of  freckles,  and  the  truer  rendering  of  light  or  golden  hair. 
For  copying  pictures  or  coloured  objects  of  any  kind  these 
plates  are  now  universally  used,  and  are  also  of  great  benefit  in 
photomicrography.  The  following  are  the  formulee  for  the  princi- 
pal baths  for  sensitising  ready-prepared  plates  :- 

Bothamley's  Process. 

Solution  of  erythrosin  (i  in  1,000)        ...  I  to  2  parts. 

Ammonia  (10  per  cent.)  ...       ...       ..  1  part. 

Water    8  parts. 

Dust  the  plate,  and  immerse  for  two  or  three  minutes.  Allow 
to  drain  on  blotting  paper,  and  dry  in  the  dark.  The  conclusions 
drawn  from  a  series  of  experiments,  and  given  by  Mr.  Bothamley 
at  the  Photographic  Convention,  1889,  were  :  "(1)  Alcohol  up  to 
10  per  cent,  has  no  influence  whatever,  and  may  be  dispensed 
with  where  the  dye  is  soluble  in  water.  Alcohol  in  larger  pro- 
portion produces  a  distinct  decrease  in  sensitiveness.  (2)  With 
a  concentration  of  the  dye  up  to  1  in  5,000,  the  washing  after 
immersion  is  totally  unnecessary.    (3)  A  preliminary  bath  may 

265 


ISO] 


DICTIONARY  OF  PHOTOGRAPHY. 


be  omitted."  It  is  as  well  to  point  out  that  the  use  of  eosin  or 
erythrosin  in  conjunction  with  ammonia  is  covered  by  Tailfer's 
process,  and  that  permission  must  be  obtained  from  the  English 
licencees  to  work  the  same. 

Vogel's  Formula. 

Azaline  tincture   i  oz.    or  29.5  c.cm. 

Distilled  water   3^  ozs:  ,,  103.25  „ 

Alcohol  or  methylated  spirit    ...  4  drms.  „     14.75  » 

Liquid  ammonia           ...       ...  1  drm.  „     3.6  „ 

Dust  the  plates,  and  immerse  for  one  minute ;  rock  during 
immersion.    Drain  on  blotting  paper,  and  dry  in  the  dark. 

Schumann's  Cyanin  Bath. 

Soak  the  plate  in  1  or  2  per  cent,  of  ammonia  solution  for  two  or 
three  minutes  ;  then  immerse  in — 

Alcoholic  solution  of 

cyanin  (1  in  500)   168  mins.  or  10  c.cm. 

Ammonia     ...       ...       ...  68  ,,  4 

Alcohol    168    ,,     „  10 

Distilled  water    7  ozs.        200  „ 

for  not  more  than  100  seconds,  drain  and  dry. 

Bothamley's  Sensitiser  for  Pictures. 

Solution  of  rose  Bengal  (1  in  1,000)      ...      10  parts. 

Solution  of  cyanin  (1  in  2,000)    10 

Solution  of  erythrosin  ( 1  in  2,000)         ...      10  ,, 

made  alkaline  with  1  per  cent,  of  ammonia.  These  are  the 
principal  baths,  and  from  these  others  may  be  used,  which  may 
be  made  on  the  above  lines.  The  usual  distinction  between  iso- 
and  ortho-chromatic  plates  is  that  the  former  are  prepared  by 
adding  the  dye  to  the  emulsion  when  making  the  same,  and  that 
the  latter  are  plates  prepared  by  bathing  after  being  coated  and 
dried.  Before  closing  this  article,  it  is  but  fair  to  state  that 
Mr.  F.  E.  Ives,  of  Philadelphia,  U.S.,  has  made  numerous  ex- 
periments with  collodio-bromide,  and  finds  that  the  best  results 
are  obtained  by  flowing  over  the  coated  plate,  as  soon  as  the 

266 


DICTIONARY  OF  PHOTOGRAPHY. 


[Kal 


collodion  has  set,  a  strong  alcoholic  solution  of  chlorophyll, 
obtained  by  digesting  blue  myrtle  or  the  periwinkle  (vinca  major) 
leaves  in  alcohol,  then  immersing  the  plates  in  water  strongly 
tinted  with  blue  shade  eosin,  and  drying.  This  process  is  said 
to  render  the  plate  sensitive  for  the  whole  range  of  the  spectrum. 

Ivory.  The  teeth  and  tusks  of  the  elephant  and  walrus. 
Photographs  can  be  obtained  on  ivory  by  coating  with  an 
emulsion  or  by  transfer  as  in  the  carbon  process. 

Ivory  Black.  Made  by  calcining  ivory  in  close  crucibles ; 
used  as  an  ingredient  for  black  varnish,  etc. 

Japan  Varnish.   See  Varnish. 

Kallitype.  A  printing  process  invented  by  Dr.  J.  Nichol,  the 
principle  of  which  was  that  ferric  salts  were  reduced  by  light 
to  ferrous,  and  in  this  condition  reduced  to  the  metallic  state  a 
soluble  silver  salt.  The  paper  is  first  sized,  then  coated  with 
either  of  the  following  solutions,  which  contains 

Sodio-citrate  of  iron  solution       ...      20  per  cent. 
Neutral  potassium  oxalate ...       ...       5   ,,  ,, 

The  sodium  salt  can  be  replaced  by  the  ammonium  or  potassium 
salts,  or  by  the  tartrate  salt,  or  by  mixtures  of  these  compounds. 
The  paper  is  printed  in  the  same  way  as  platinotype,  and 
developed  for  bluish  tones  on  a  solution  containing 

Potassium  oxalate   20  per  cent. 

Silver  nitrate    1*5   ,,  ,, 

to  which  sufficient  ammonia  is  added  to  dissolve  the  precipitate 
first  formed.    For  neutral  black  tones  a  solution  containing 

Potassium  oxalate   10  per  cent. 

Silver  nitrate   ...     1*5  M 

and  ammonia  is  used.    For  sepia  tones  a  solution  containing 

Borax   7  per  cent. 

Silver  nitrate   ...       ...     15    ,,  ,, 

Ammonia  as  above,  is  used.  Good  results  may  also  be  obtained 
by  sensitising  with 

Ferric  oxalate    ...  5  per  cent. 

Ferric  tartrate    5  ,, 

Oxalic  or  tartaric  acid    1    „  „ 

267 


Kal]  DICTIONARY  OF  PHOTOGRAPHY. 

For  developing  this  either  of  the  two  following  solutions  is  used : — 

I. 

Potassium  citrate   15  per  cent. 

Sodium  acetate      ...       ...       ...      10  M  „ 

Silver  nitrate  ...    1*5  „ 

Ammonia  to  dissolve  the  precipitate  first  formed. 

Potassium  citrate    15  per  cent. 

Potassium  oxalate  ...       ...       ...      10  „  ,, 

Silver  nitrate    1-5 

Ammonia  as  above.  After  development  the  prints  should  be 
placed  in  a  clearing  bath  of  a  20  per  cent,  solution  of  citrate  or 
tartrate  of  potassium,  sodium  or  ammonium  rendered  alkaline  by 
liquid  ammonia.  If  greater  contrasts  are  desired,  2  to  10  parts 
of  a  5  per  cent,  solution  of  potassium  bichromate  should  be  added 
to  every  1000  parts  of  the  developer.  A  modification  of  the 
process  was  published  later,  in  which  the  silver  was  incorporated 
with  the  sensitising  solution,  and  applied  to  the  paper,  the  solu- 
tion being  a  mixture  of  ferric  oxalate,  ferric  tartrate,  oxalate  and 
nitrate  of  silver,  and  free  nitric  acid.  The  prints  were  deveLoped 
on  the  following  solutions  : — 

For  Black  Tones. 

Rochelle  salts    10  parts. 

Borax   10  „ 

Water    200 

For  Purple  Tones. 

Rochelle  salts    10  parts. 

Borax   2-5  ,, 

Water    100  „ 

For  Sepia  Tones. 
Rochelle  salts        ...       ...       ...       ...       5  parts. 

Borax   175  part. 

Water  ...       ...       ...       ...       ...  100  parts. 

Hydrochloric  acid   a  few  drops. 


To  the  developers  a  few  drops  of  a  dilute  solution  of  potassium 

268 


DICTIONARY  OF  PHOTOGRAPHY. 


[Lea 


bichromate  were  added  to  keep  the  prints  clean,  and  to  increase 
contrasts  ;  after  development,  they  were  immersed  in  a  solution  of 

Rochelle  salts        ...       ...       ...       ...      10  parts. 

Water  100  ,, 

and  then  in 

Water    80  parts. 

Ammonia    ...       ...       ...       1  part. 

and  subsequently  washed  and  dried. 

Kaolin.  Synonym :  China  Clay.  A  very  fine  hydrous 
silicate  of  alumina,  containing  about  14  per  cent,  of  water.  It 
is  a  decomposition  product  from  natural  decay  of  felspar.  It 
is  used  for  cleaning  plates,  and  was  used  in  the  old  wet  process 
as  a  mechanical  purifier  of  the  silver  bath. 

Lac.    See  Shellac. 

Lamp.  Well  known  as  the  source  of  artificial  illumination 
in  the  dark-room.  All  lamps  should  be  fitted  with  one  or  more 
screens  of  ruby  or  orange  glass,  so  as  to  decrease  or  increase 
the  light  as  desired.  As  some  amateurs  may  desire  to  rig  up  a 
temporary  lamp  whilst  on  tour,  the  following  suggestions  may 
be  useful : — Every  amateur  should  comprise  amongst  his  travel- 
ling paraphernalia  one  or  two  square  feet  of  ruby  or  golden 
fabric ;  by  means  of  this  a  lamp  may  be  improvised  from  an 
ordinary  candle,  or  night-light,  or  a  Chinese  lantern,  or  the 
side  may  be  knocked  out  of  a  card-board  hat-box.  The  author 
has  before  now  changed  plates  when  away  from  home  by  the 
aid  of  this  little  piece  of  ruby  cloth  by  placing  a  candle  in  the 
empty  fire-grate,  and  the  ruby  cloth  over  the  bars. 

Lampblack.  The  very  light  form  of  carbon  produced  by 
burning  pitch,  resin,  or  any  other  smoky  substance  with  limited 
access  of  air,  and  collecting  the  soot  formed. 

Landscape  Lens.   See  Lens. 

Lantern,  Optical.   See  Magic-Lantern. 

Lantern  Slides.   See  Transparencies. 

Latent  Image.   See  Image,  Latent. 

Lead,  Acetate  of,  (Ger.,  Essigsdures  Blei;  Fr.,  Acetate  de 
269 


Lea] 


DICTIONARY  OF  PHOTOGRAPHY. 


plomb;  Ital.,  Acetato  di  piombo).  Pb(H3C202)2,3H20  =  379. 
Synonyms  :  Plumbic  Acetate,  Sugar  of  Lead.  Made  by  dissolving 
litharge  in  an  excess  of  acetic  acid  and  subsequent  purification 
and  crystallisation.  It  is  met  with  in  white  crystals  usually 
massed  together  which  have  an  intensely  sweet  taste,  and  smell 
faintly  of  acetic  acid.  It  is  used  as  an  addition  to  some  combined 
toning  and  fixing  baths,  and  has  been  suggested  as  a  hypo- 
eliminator  but  the  benefit  is  doubtful.  Solubility ;  60  per  cent, 
in  cold  and  200  per  cent,  in  hot  water  ;  12  per  cent,  in  alcohol ; 
insoluble  in  ether. 

Lead,  Chr ornate  of  (Ger.  Bleichromat ;  Fr.,  Chr ornate  de 
plomb;  Ital.,  Cromato  di  piombo).  PbCr04  =  323*5.  Prepared 
by  double  decomposition  of  lead,  acetate,  and  chromate  of 
potassium.  It  is  a  yellow  insoluble  powder,  and  is  only  used  as 
colouring  matter  for  certain  dark  room  fabrics. 

Lead,  Nitrate  of  (Ger.,  Bleinitrat;  Fr.,  Azotate  de  plomb;  Ital., 
Azotato  di  piombo).  Pb(N03)2  =  331.  Synonym  :  Plumbic 
Nitrate.  Made  by  dissolving  litharge  or  white  lead  in  nitric  acid, 
evaporating  and  crystallising.  It  occurs  in  hard,  white,  opaque, 
octahedral  crystals.  It  is  used  in  intensification  (q.v.)  as  a 
constituent  of  some  combined  toning  and  fixing  baths. 

Lead,  Toning  with.  A  solution  of  acetate  of  lead  has  been 
proposed  as  a  toning  bath  for  albumenised  and  gelatino-chloride 
papers.    The  following  formula  has  been  suggested : — 

Lead  acetate  or  nitrate      ...       ^  oz.  or   15  grms. 
Sodium  hyposulphite        ...       4  ozs.  „  120  „ 
Distilled  water    20  ,,     ,,  500  c.cm. 

The  toning  action  in  any  bath  of  this  character  is  entirely  due 
to  sulphuration  as  described  under  Combined  Toning  and 
Fixing  (q.v.). 

Least  Circle  of  Aberration  is  the  smallest  possible  section 
of  the  cone  of  rays  of  light  emergent  from  a  lens.  Practically  it 
is  the  nearest  approach  to  a  perfect  focus  that  parallel  rays  of 
light  can  have. 

Leimtype.  A  special  process  for  the  production  of  half-tone 
blocks  invented  by  Husnik  of  Prague,  the  particulars  of  which 
have  never  been  published. 

270 


DICTIONARY  OF  PHOTOGRAPHY.  [Ldl 

Lens.  An  optical  term  given  to  discs  of  glass  bounded  by  two 
spherical  surfaces,  or  by  a  plane  and  a  spherical  surface.  A  true 
lens  is  one  which  has  the  form  shown  in  fig.  47,  a ;  but  the  name 
now  includes  many  other  shaped  glasses  or  combination  of  glasses 
from  the  analogy  of  their  action  upon  light.  The  first  mention 
of  the  use  of  a  lens  which  I  have  been  enabled  to  trace  out  is  by 
the  Chinese  moralist  Confucius,  748  B.C.,  who  says,  "  As  we  use 
a  glass  to  examine  objects,  so  must  we  look  to  the  present  for 
futurity."  In  the  Western  classics,  about  a.d.  40,  mention 
is  made  by  Seneca,  Aristophanes,  and  other  writers  for  the 
first  time  of  globes  of  water  and  globes  of  glass  ;  but  of  a  true 
lens  absolutely  no  mention  is  made,  and  it  is  even  doubtful 
whether  they  were  more  than  conversant  with  the  burning 
powers  of  the  above  globes.  There  is,  however,  in  the 
Assyrian  Section  of  the  British  Museum  a  piece  of  rock-crystal 
of  plano-convex  form,  which  Sir  David  Brewster  states  was 
designed  for  magnifying.  It  has  been  shaped  oval,  evidently 
by  a  process  of  chipping  and  grinding,  and  both  plane  and 
convex  surfaces  have  been  partly  polished.  It  seems  more  likely, 
however,  that  it  was  used  as  an  ornament.  The  date  of  this  is 
about  720  B.C.  There  are  also  in  the  British  Section  several 
antique  glass  bosses,  which  have  been  evidently  polished  and  cut 
to  a  wonderfully  true  curve.  These,  however,  it  is  supposed, 
were  used  for  ornamenting  shields,  sword-handles,  etc.  The 
first  lenses  that  we  can  find  any  really  reliable  record  of  are 
of  those  of  spectacles,  and  these  are  mentioned  by  Giordano 
da  Rivalto  in  1305,  as  having  been  invented  only  "  twenty  years 
ago."  This  will  fix  the  date  at  1285,  when  they  were  invented  by 
Salvino  d'Armati,  a  Florentine.  Like  some  of  those  who  have 
followed  in  his  footsteps  in  the  present  day,  he  desired  to  make  his 
fortune  by  this  invention  or  discovery  by  keeping  the  same  secret ; 
but  the  patent  laws,  unfortunately  for  him,  were  not  quite  so 
well  developed  as  at  the  present  time  ;  and  a  scientist  of  Pisa, 
Alessandro  della  Spina,  having  seen  some  of  Armati's  spectacles, 
made  some  for  himself,  and  published  the  method  of  manufacture. 
The  gradual  and  perhaps  accidental  deepening  of  the  curves 
of  these  lenses  produced  shorter  foci,  till,  by  the  accidental 
placing  at  some  distance  apart  of  a  concave  and  convex  lens  by 
some  children  of  a  Dutch  spectacle  maker,  the  telescope  was 
discovered,  and  from  this  origin  all  lenses  of  the  present  day 

27  1 


Leil]  DICTIONARY  OF  PHOTOGRAPHY. 

have  been  evolved.  All  lenses  are  made  of  crown  or  flint  glass, 
the  former  being  free  from,  and  the  latter  containing  lead,  the 
flint  being  slightly  more  refractive  than  the  crown.  The  sectional 
forms  of  the  various  lenses  are  here  given  : — 


a  I  c 


Fig.  47.— a,  double-convex  ;  b,  plano-convex  ;  c,  concavo-convex,  or  converging 
meniscus ;  d,  double-concave  ;  e,  plano-concave  ;  /,  divergent  meniscus. 

The  first  three,  a,  &,  c,  which  are  thicker  at  the  centre  than  at 
the  margins,  are  convergent  or  positive ;  and  the  second  three, 
d,  e,ft  are  divergent  or  negative.  All  lenses  are  formed  by  the 
union  of  prisms,  and  therefore  have  to  a  great  extent  the  pro- 


Fig.  48. 

perties  of  prisms.  Fig.  48  will  show  the  way  in  which  the  prisms 
are  united  to  form  a  biconvex  lens,  and  the  concentration  of  the 
rays  of  light  by  such  prisms  or  lens.  Fig.  49  is  the  representation 
of  the  prisms  forming  a  double- concave,  and  the  divergent  action 
of  such  prisms  or  lens  upon  the  rays  of  light.    It  is  obvious  that 

272 


DICTIONARY  OF  PHOTOGRAPHY. 


[Len 


by  combining  the  two  lenses  the  convergent  or  positive  action  of 
the  one  may  be  counteracted  by  the  divergent  or  negative  action 
of  the  other.  It  is  upon  these  principles  that  the  whole  of  the 
modern  lenses  are  calculated.  As  soon  as  it  was  announced  in 
1830  by  Daguerre  and  Fox  Talbot  that  they  had  been  enabled  to 
obtain  a  comparatively  permanent  image  in  the  camera  obscura, 


Fig.  49. 


the  ability  and  skill  of  mathematicians  and  opticians  were  brought 
into  play  to  produce  lenses  which  should  be  free  from  the 
objections  common  to  the  double-convex  lens,  which  was  the 
only  one  used  in  the  camera  obscura  in  those  days.  The  single 
lens  was  replaced  by  the  achromatic  combination  of  the  telescope. 
This  was  eventually  reversed,  and  the  plane  side  presented  to 


Fig.  50.  Fig.  51. 


the  object,  as  in  fig.  50-  Then  Wollaston's  meniscus  (fig.  5-)  came 
to  be  recognised  as  a  means  of  extending  the  definition  ;  and  in 
1840,  Chevalier,  a  Paris  optician,  still  further  improved  it  by  a 
different  method  of  achromatising  the  lens.  But  in  the  following 
year,  through  the  agency  of  Voigtlander,  a  practical  optician,  a 
lens  designed  by  Professor  Petzval,  a  mathematician  of  Vienna, 
was  made  and  introduced  commercially  in  1841.    This  was  the 

273  X 


Len]  DICTIONARY  OF  PHOTOGRAPHY. 

portrait  lens ;  and  it  is  a  remarkable  fact  that  it  is  the  model  for 
the  finest  portrait  lenses  of  the  present  day.    The  following 


Fig.  52.  Fig.  53. 


(fig.  53)  is  a  sketch  of  Petzval's  original  portrait  lens  : — The  dark 
shaded  parts  are  crown,  the  light  shaded  parts  are  flint  glass, 
and,  as  will  be  seen,  the  front  combination  exists  of  a  double- 


Fig.  54.  FiS-  5,5- 


convex  crown  cemented  to  a  double-concave  flint,  and  the  back 
of  a  flint  concavo-convex  separated  from  a  double -convex  lens  of 
crown  glass ;  the  flint  concavo-convex  having  such  a  negative 

274 


DICTIONARY  OF  PHOTOGRAPHY.  [Len 

refractive  power  as  to  completely  balance  the  positive  aberration 
of  the  whole  combination.  This  has  been  modified  by  Dallmeyer, 
by  Grubb,  and  the  noted  American  optician  Morrison  ;  but  all 


Fig.  5fi. 


are  constructed  on  the  principle  of  above  lens  (fig.  53).  Professor 
Petzval  calculated  at  the  same  time  a  landscape  lens  (fig.  54), 
which  was  not  introduced  commercially  till  1857  ;  and  an  English 


Fig.  57-  Fig.  58. 


optician,  in  1858,  introduced  a  lens  having  a  concave  glass  in 
place  of  the  diaphragm  to  lengthen  the  focus  and  flatten  the 
field,  and  Dallmeyer  introduced  his  famous  triplet  (fig.  55), 
which  was  much  used  and  admired.    Single  lenses  were  firs 

275  1 


Lenj 


DICTIONARY  OF  PHOTOGRAPHY. 


of  all  of  the  kind  shown  in  fig.  51,  with  which  extremely  small 
diaphragms  are  necessary  to  reduce  spherical  aberration  and 
distortion.  This  was  improved  on  by  Grubb,  and  his  lens 
is  shown  in  fig.  56,  in  which  a  crown-glass  lens  of  meniscus 
form  is  presented  to  the  object,  and  is  cemented  to  a  flint 


Fig.  59.  Fig.  60. 


meniscus.  This  gave  a  much  flatter  field,  and  spherical  aber- 
ration was  much  reduced,  allowing  the  use  of  larger  dia- 
phragms. Dallmeyer  introduced  his  single  lens  (fig.  57),  which 
consists  of  a  negative  flint  enclosed  between  two  positive  crown- 
glass  lenses.   1  This  enabled  a  much  larger  aperture  to  be 


FiS-  61.  Fig.  62. 


employed,  and  totally  eliminated  spherical  aberration.  Marginal 
definition  and  flatness  of  field  were  both  improved.  To  obviate 
distortion,  many  doublet  lenses  were  introduced,  that  of  Mr.  Ross 
being  shown  in  fig.  58.  This  instrument  possesses  a  wide  angle, 
giving  splendid  definition,  without  any  distortion  or  aberration, 
In  all  doublets  the  diaphragm  being  placed  between  the  combina- 

276 


DICTIONARY  OF  PHOTOGRAPHY. 


[Len 


tions,  the  distortion  of  the  one  is  cured  by  the  distortion  of  the 
other.  In  i860  Harrison  of  New  York  introduced  his  globe 
lens  (fig.  59),  which  had  an  extremely  wide  angle,  but  which,  from 
too  close  an  adherence  to  the  globe  form,  gave  a  flare.  Busch 
improved  upon  this  with  the  pflntoscope  (fig.  60),  and  Dallmeyer 


Fig.  63. 


introduced  his  wide-angle  rectilinear  (fig,  61).  Steinheil  intro- 
duced what  he  called  his  periscopicjens  (fig.  62),  which  consists 
of  two  uncorrected  meniscus  lenses  of  crown  glass ;  and  chro- 
matic aberration  not  being  eliminated,  the  focussing  screen  had 
to  be  brought  nearer  to  the  lens  after  focussing  and  before 


exposing,  by  ^  of  the  focal  length  of  lens.  Mr.  Sutton's  panora- 
mic lens  (fig.  63)  consisted  of  two  concavo-convex  lenses,  with 
spherical  curvatures  and  a  hollow  space  between  filled  with 
water.  This  possessed  a  wide  angle,  and  gave  no,  or  practically 
no,  spherical  or  chromatic  aberration,  but  from  its  peculiar  con- 
struction, and  the  necessity  of  using  curved  plates,  has  never 

277 


Len] 


DICTIONARY  OF  PHOTOGRAPHY. 


come  into  general  use.  In  figs.  64,  65,  and  66  are  shown  lenses 
by  Steinheil,  fig.  64  being  an  aplanatic  rapid  rectilinear,  and  figs. 
65  and  66  wide-angle  aplanats,  some  of  the  finest  lenses  of  the 
day ;  and  in  figs.  67  and  68  are  shown  two  more  of  Steinheil's 
lenses,  which  work  at //2*5,  No.  67  being  for  groups,  No.  68  for 
portraits.    In  fig.  69  I  am  enabled,  by  the  kindness  of  Messrs. 


Fig.  66. 


Perken,  Son,  &  Rayment,  to  give  a  sketch  of  the  Euryscope 
lens,  which  is  composed  of  two  symmetrical  combinations  of 
flint  glass,  and  works  at  an  aperture  of  //6,  a  great  gain  for  rapid 
work.  These  lenses  are  perfectly  free  from  spherical  and  chro- 
matic aberration  and  distortion,  and  for  such  a  large  aperture 
have  a  wonderful  depth  of  focus,  with   an  extremely  flat 


Fig.  67.  Fig.  68. 


field.  Mr.  Dallmeyer  has  introduced  a  rectilinear  or  non- 
distorting  single  lens,  which  works  at  a  large  aperture,  which 
is  absolutely  free  from  distortion,  without  astigmatism,  and 
a  very  flat  field  (fig.  70).  Thus  far  I  have  endeavoured  to  give 
some  slight  sketch  of  the  leading  and  fundamental  forms  of  all 
lenses,  and  whilst  numerous  modifications  exist  which  may  be 
considered  advantageous  by  some,  they  are  all  made  on  the 
principles  involved  in  one  of  the  above.    A  lens,  or  rather  a 

278 


DICTIONARY  OF  PHOTOGRAPHY. 


[Len 


doublet  lens,  is  said  to  be  symmetrical  when  both  combinations 
are  precisely  alike  and  possess  the  same  optical  properties.  In 
all  such  combinations  the  diaphragm  is  placed  midway  between 
the  two.    Non-symmetrical  lenses  are  those  in  which  one  of  the 


Fig.  69. 


combinations  is  the  more  powerful  in  some  way  or  other,  in 
which  case  the  diaphragm  is  placed  at  the  exact  proper  distance 
as  calculated  by  the  optician.  To  enable  the  amateur  to  select 
a  lens  for  his  own  use,  several  considerations  are  necessary,  and 


Fig.  70. 


although  he  may  be  to  some  extent  guided  by  the  vendor  of  the 
lens,  the  following  may  be  of  some  assistance : — The  lens  should 
be  absolutely  free  from  striae  ;  these  can  be  detected  by  placing 
the  eye  at  the  focus  of  a  lens  before  a  strong  light  such  as  gas  or 

279 


Len] 


DICTIONARY  OF  PHOTOGRAPHY. 


a  lamp  ;  bubbles  can  also  be  seen,  but  too  much  stress  need  not 
be  laid  on  the  presence  of  one  or  two  bubbles,  as  when  not 
present  in  very  large  numbers  they  may  be  disregarded.  For 
what  purpose  is  the  lens  required?  For  ordinary  landscape 
work,  architectural  subjects,  interiors,  or  portraits  ?  For  landscape 
work  pure  and  simple  there  are  few  lenses  to  equal  the  achromatic 
single  landscape  lens,  which  gives  brilliant  negatives ;  and 
although  distortion  is  present  it  may  be  disregarded,  and  it  is 
practically  unnoticeable  in  small  views  except  by  mathematical 
measurement.  Some  of  these  lenses  are  now  made  to  work 
aplanatic  with  an  aperture  of  //8,  and  are  therefore  of  nearly  the 
same  rapidity  as  the  rapid  rectilinear,  which  is,  however,  the  lens 
par  excellence  for  amateurs,  as  its  use  is  practically  unlimited, 
especially  as  some  are  now  made  to  work  at  almost  as  large  an 
aperture  as  a  portrait  lens.  Few  amateurs  will  require  a  portrait 
lens,  as  they  are  not  only  difficult  to  use  properly,  but  are 
exceedingly  limited  in  action,  and  also  expensive.  The  question 
of  how  much  view  to  include  on  a  plate  is  another  important 
consideration  which  should  not  be  lost  sight  of  (See  Angle, 
Width  of)  ;  for  ordinary  work  it  should  never  exceed  5o°to  550, 
and  450  is  decidedly  better,  as  this  is  about  the  angle  included  by 
the  human  eye.  If  a  much  greater  angle  be  included,  the  result* 
ing' pictures  have  a  distorted  appearance,  because  it  is  extremely 
unlikely  that  the  eye  will  be  placed  at  a  focal  length  of  the  lens 
from  the  picture.  The  glass  of  which  lenses  are  made  should  be 
absolutely  colourless ;  this  can  be  tested  by  laying  the  lens  upon 
a  sheet  of  white  paper  and  looking  down  through  it.  Some  of 
the  cheaper  lenses  are  made  of  glass  which  is  not  colourless  :  and 
any  colour,  especially  brown  or  yellow,  will  make  the  lens  slow. 
As  stated  under  the  article  Glass,  it  is  absolutely  necessary  to 
obtain  it  perfectly  homogeneous,  free  from  striae,  colourless,  and 
transparent ;  bubble,  lines,  and  opaque  particles  in  lenses  merely 
obstruct  a  certain  amount  of  light,  but  striae  prove  imperfect 
and  unequal  mixture  of  the  substances  composing  it,  and  will 
therefore  give  different  refractions.  The  glass  is  made  in  the 
following  manner  : — Crucibles  of  fire-clay  of  particular  form  are 
raised  to  a  white  heat  in  a  furnace,  and  when  the  fuel  ceases  to 
give  off  smoke,  they  are  charged  with  the  materials,  and  the  heat 
is  continued  for  eight  or  ten  hours.  The  crucible  is  now  raised 
to  a  white  heat  for  four  hours,  and  the  mixture  stirred  with  a  bar 

280 


DICTIONARY  OF  PHOTOGRAPHY.  [Leu 

of  potter's  clay.  Six  times  from  hour  to  hour  the  mixture  is 
stirred.  The  heat  is  then  reduced,  that  the  bubbles  may  rise, 
and  again  at  the  end  of  two  hours  the  heat  is  raised  to  make  the 
glass  fluid  ;  again  stirred  for  two  hours,  and  the  crucible  and  the 
openings  of  the  furnace  closed  and  left  for  eight  days  to  cool. 
The  crucible  is  taken  out  and  broken,  and  the  glass  is  removed 
and  divided  into  pieces.  The  divided  glass  is  examined  and 
sorted,  the  finest  being  retained  for  astronomical  purposes,  the 
second  quality  for  photographic  lenses,  and  the  third  for  ordinary 
magnifying  glasses,  the  rest  being  waste,  which  is  added  to  the 
next  melting.  The  pieces  are  then  softened  in  a  muffle  furnace, 
and  formed  into  plates  about  two  or  two  and  a  half  inches  thick. 
Sometimes  the  plates  are  then  cast,  after  being  softened  by  heat, 
into  rough  moulds  of  clay  or  iron  coated  with  sand  so  as  to  give 
them  a  rough  form  ;  but  the  best  opticians  prefer  grinding,  as  striae 
and  bubbles  are  not  so  liable  to  be  formed,  except  with  condens- 
ing lenses  in  which  striae  and  bubbles  are  not  of  so  much  impor- 
tance. The  rough-shaped  glasses  have  now  to  be  made  into 
perfect  lenses,  for  which  purpose  extreme  care  is  absolutely 
necessary,  approximate  forms  being  given  by  grinding  with  emery 
in  concave  or  convex  tools  of  cast  iron.  It  is  in  the  follow- 
ing operations  that  the  greatest  skill  and  care  of  the  optician  are 
required  : — The  roughly  shaped  lens  is  now  to  be  ground  with 
emery  in  spherical  tools  of  brass  or  iron,  which  tools  are  made 
either  by  casting,  or  by  rough  casting  and  subsequent  work  in  a 
lathe.  These  are  given  the  necessary  curves  by  means  of  extremely 
accurate  gauges  of  copper.  The  roughly  fashioned  glass  or  lens 
is  fixed  to  a  plate  of  brass  by  means  of  pitch,  and  is  then  worked 
in  the  tool  with  rough  emery  moistened  with  water;  when  the  glass 
is  found  to  touch  the  tool  at  all  points,  finer  emery  is  used,  and  it 
is  worked  a  little  more,  the  gauge  being  now  frequently  applied 
to  the  tool,  to  see  that  the  radii  of  curvatures  are  not  altered  ; 
then  finer  kinds  of  emery  still  are  used,  till  at  last  some  degree 
of  polish  begins  to  show  ;  fine  putty  powder  is  then  substi- 
tuted for  emery,  and  the  polishing  is  begun.  The  operation  of 
polishing  is  really  the  test  of  a  good  optician,  as  this  process  may 
alter  the  sphericity  or  the  radii  of  curvature  of  the  lens  to  such  a 
degree  as  to  completely  alter  the  character  of  the  lens.  The  lens 
is  fixed  on  to  a  block  of  wood  by  means  of  a  pitchy  cement,  and 
a  tool  is  coated  with  a  resinous  mixture,  and  fine  rouge  is  sprinkled 

281 


Len] 


DICTIONARY  OF  PHOTOGRAPHY. 


on  the  tool  when  cold,  and  the  polishing  finished  entirely  by  hand. 
When  two  lenses  are  required  to  be  cemented  together  so  as 
to  present  one  common  surface,  they  are  slightly  warmed,  and  a 
drop  or  two  of  Canada  balsam  is  applied,  and  the  two  lenses 
pressed  forcibly  together,  so  as  to  squeeze  out  excess  of  balsam. 
When  cooled,  they  present  the  appearance  of  one  single  piece  of 
glass,  and  cannot  be  separated  without  heat.  When  two  lenses 
have  not  a  common  surface,  three  small  pieces  of  tinfoil  are 
introduced  at  equal  distances  apart  between  their  margins,  or 
when  the  separation  is  greater,  as  in  most  portrait  lenses,  a  ring 
of  brass  is  used  for  the  same  purpose.  When  the  lens  is  fixed 
in  its  brass  ring,  so  that  it  cannot  be  taken  out  without  raising 


the  bent  edge  of  the  brass,  it  is  said  to  be  set.  Under  the 
article  Focus  will  be  found  numerous  rules  and  tables,  which 
may  be  of  some  service.  Since  the  article  on  lenses  was  originally 
written  great  advances  have  been  made,  and  new  forms  of  lenses 
have  been  introduced,  in  the  majority  of  which  the  new  optical 
glass  manufactured  at  Jena  is  employed.  The  following  are  the 
principal  novelties,  and  in  those  cases  in  which  diagrams  are 
given  I  am  indebted  to  the  makers  or  agents  for  the  same. 
Messrs.  Swift  &  Sons'  new  lenses  are  fig.  71,  a  universal  paragon 
lens  working  at  U.S.  No.  2  or y 5*65,  and  fig.  72,  Swifts  portrait 
paragon,  a  symmetrical  lens,  working  at  U.S.  No.  I,  or  //4,  the 
combinations  of  this  lens  being  of  the  new  Jena  glass.  E.  Suter  of 
Basle  has  a  series  of  aplanatic  lenses,  which  work  at  U.S.  No.  2, 


Fig.  71. 


282 


DICTIONARY  OF  PHOTOGRAPHY. 


[Len 


and  also  a  very  fine  lens  of  the  symmetrical  type,  manufactured 
of  the  new  glass,  which  works  at  No.  2  U.S.,  or //$'$.   With  these 


Fig.  72. 


the  flatness  of  field  is  much  increased,  the  angle  of  sharpness 
being  about  6o°.     He  has  also  introduced  a  new  wide-angle 


Fig-  73- 


aplanat,  which  has  an  effective  aperture  of //12  for  an  angle 
of  6o°,  and  //16  and  //22  up  to  90°  a  diagram  (fig.  73)  of 
which  I  am  enabled  to  give  by  the  kindness  of  Mr.  Gotz,  the 

283 


Len] 


DICTIONARY  OF  PHOTOGRAPHY. 


English  agent.  The  field  of  this  lens  is  very  flat,  and  the  front 
lens  may  be  used  as  a  single  landscape  by  unscrewing  the  same, 
and  screwing  into  the  place  of  the  back  lens.  The  front  combi- 
nation is  of  Jena  flint  combined  with  crown  glass,  and  of  great 
curvature,  whilst  the  back  glass  is  of  much  less  power.  Messrs. 
Taylor,  Taylor  &  Hobson,  Wray  &  Swift  have  introduced  special 
lenses,  which,  in  the  smaller  sizes,  work  at  f/$'6  for  detective 
cameras,  although  any  of  the  above  lenses  of  sufficiently  short 
focus  would  answer  equally  as  well.  Messrs.  Perken,  Son,  & 
Rayment  have  issued  a  new  wide-angle  euryscope,  working  at 


Fig-  74- 


//c/5  ;  and  Messrs.  Voigtlander  &  Son  have  introduced  two  new 
wide-angle  lenses,  the  one  a  landscape,  composed  of  a  bi-convex 
crown  cemented  to  a  bi-concave  lens.  Both  glasses,  of  the  new 
Jena  material,  are  extremely  light,  and  of  little  dispersive  power, 
in  great  disproportion  to  the  index  of  refraction ;  thus  the  bi- 
concave lens,  which  is  usually  a  flint,  is  more  like  a  crown  glass 
lens.  It  subtends  an  angle  of  76°  has  an  exceedingly  flat 
field,  and  distortion  of  the  marginal  lines  is  reduced  to  a 
minimum  ;  working  aperture,  //16.  The  other  lens  is  a  new 
wide-angle  euryscope,  which  works  at  f/6  (approx.),  and  includes 

284 


DICTIONARY  OF  PHOTOGRAPHY.  [Len 

an  angle  of  8o°.  This  also  is  constructed  of  the  new  glass. 
From  its  large  aperture  and  short  focus  it  is  eminently  suited  for 
group  work  in  confined  situations,  and  for  instantaneous  or  hand 
cameras.  In  1889  Ross  &  Co.  obtained  a  patent  for  a  new  form 
of  lens,  which  they  called  the  "  Concentric,"  from  the  fact  that 
the  internal  and  external  surfaces  of  each  combination  were  struck 
from  a  common  centre,  as  shown  in  fig.  74.  It  will  be  seen  that 
these  lenses  are  practically  what  would  with  the  old  glasses  be 
negative  lenses — that  is,  they  are  thinner  in  the  middle  than  at 
the  margins  ;  but  by  the  use  of  particular  kinds  of  Jena  glass  the 
manufacture  of  such  combinations  with  a  positive  focus  was 
rendered  possible.  The  advantage  of  these  lenses  lies  in  the  fact 
that  they  are  free  from  chromatic  aberration  and  astigmatism ; 
and  a  lens  the  focus  of  which  is  one-third  less  than  the  longer 
base  line  of  the  plate  covers  that  plate  sharply  with  //19.  Some 
of  the  lenses  are  made  to  work  at  //16,  and  at  this  aperture  they 
give  a  general  softness  of  definition,  which  is  exceptionally 
pleasing.  The  only  disadvantage  is  that  focussing  must  be  done 
with  the  aperture  which  is  to  be  used  for  exposing  with.  These 
lenses  possess  a  flatness  of  field  which  is  very  remarkable.  Zeiss 
of  Jena  has  introduced  several  new  forms  of  lenses,  all  constructed 
of  Jena  glass,  and  possessing  a  freedom  from  astigmatism  and 
chromatic  aberration.quite  remarkable.  Several  opticians  have  also 
introduced  telephotographic  lenses — that  is,  lenses  which,  with 
moderate  extension  of  the  camera,  give  much-enlarged  images. 

The  lens  is  the  most  important  and  at  the  same  time  the 
most  expensive  part  of  a  photographer's  outfit.  Too  much 
care  cannot  be  taken,  therefore,  in  choosing  or  in  keeping  the 
same.  Lenses  should  always  be  kept,  when  not  in  use,  in  a 
leather  case,  or  else  in  a  tin  box  padded  with  wool  or  washleather 
to  prevent  the  access  of  light,  air,  and  dust.  The  inside  of  the 
lens-tube  and  the  diaphragms  should  be  occasionally  re-blackened 
to  avoid  disturbing  reflections.  If  the  lenses  become  dusty  or 
somewhat  dim,  they  should  be  most  carefully  and  tenderly  wiped 
with  a  piece  of  soft  silk  or  washleather,  and  when  it  is  necessary 
to  clean  the  internal  surfaces  of  lenses  (doublets,  portraits,  etc.), 
it  is  advisable  to  remove  one  combination  and  clean  it,  and  then 
replace  it  before  unscrewing  another  combination  to  clean  ;  by 
this  means  displacement  of  the  combination  cannot  take  place. 
With  some  old  lenses  a  peculiar  tree-like  marking  makes  its 

285 


I*en]  DICTIONARY  OF  PHOTOGRAPHY. 

appearance,  which,  to  uninitiated  eyes,  appears  to  be  in  the 
middle  of  the  glass.  This  is  due  to  the  balsam,  which  is  used  in 
cementing  the  glasses  of  the  combination  together,  becoming  old 
and  starring.  In  such  a  case  it  is  advisable,  if  the  lens  is  worth 
anything  at  all,  to  send  it  to  an  optician,  who  will  unset  the  lens 
and  properly  re-cement  and  reset  it :  if  the  lens  is  not  of  much 
value,  and  the  owner  is  desirous  of  trying  his  hand  at  a  practical 
remedy,  the  lens  should  be  placed  in  some  methylated  spirit  or 
turpentine  in  a  water-bath  and  gradually  heated,  when  the  cement 
will  be  softened.  The  two  glasses  can  then  be  taken  apart,  well 
wiped  and  cleaned,  and  re-cemented  by  a  drop  or  two  of  Canada 
balsam,  and  gently  warming.  If  by  accident  one  of  the  lenses 
should  be  scratched,  it  is  preferable  to  fill  the  scratch  with  black 
varnish,  as  the  loss  of  light  is  in  this  case  preferable  to  the  dis- 
turbing reflections  of  the  scratch.  The  following  notes  on  choos- 
ing and  testing  a  lens  are  written  from  a  practical  standpoint,  and 
if  an  accurate  scientific  examination  is  required,  it  would  be 
advisable  to  send  the  lens  to  the  Testing  Department  at  Kew ; 
but  if  a  lens  answers  successfully  to  the  tests  described  below,  it 
may  be  accepted  as  practically  perfect.  The  first  point  to  decide 
in  choosing  a  lens  is  to  determine  for  what  class  of  work  it  will 
be  required ;  but  presuming  that  my  readers  are  amateurs,  and 
that  many  of  them  will  be,  or  have  to  be,  content  with  one  lens, 
then  a  doublet  or  rapid  rectilinear  should  be  chosen.  Perhaps  it 
would  be  advisable  to  state  for  the  benefit  of  those  who  are 
totally  ignorant  of  the  different  forms  of  lenses,  that  there  are 
three  main  classes  in  lenses:  (i)  portrait  lenses,  specially  con- 
structed for  the  requirements  of  portraiture  ;  (2)  doublet  or  rapid 
rectilinear  lenses,  which  are  constructed  for  architectural  work, 
groups,  copying,  and  landscapes,  and  may  be  termed  universal 
lenses ;  (3)  landscape  or  single  lenses,  which  are  most  suitable 
for  pure  landscape  work.  We  have  recommended  the  doublet  lens 
for  all-round  work  for  the  amateur  as  the  most  suitable  lens,  and 
which  may  be  used  for  portraits,  groups,  architectural  work,  both 
exterior  and  interior,  and  landscapes.  The  next  point  to  decide 
is  the  focal  length  of  the  lens;  this  is  usually  fixed  by  the 
optician  at  a  certain  length,  which  increases  with  the  size  of 
plate  for  which  the  lens  is  required.  The  following  may  be 
assumed  to  be  the  focal  length  of  the  majority  of  commercial 
lenses  for  the  given-sized  plates  : — 

286 


DICTIONARY  OF  PHOTOGRAPHY.  [Len 


For 

4i  x 

3i  or  £-plate,  the  lens  is  usually  4  to 

5-in.  focus. 

For 

5  x 

4 

6  „ 

For 

6£x 

4£  or  Opiate, 

8  „ 

9 

For 

7  X 

5 

9  ,» 

10  „ 

For 

*h  x 

6£  or  y-plate, 

10  „ 

11 

For 

IO  x 

8 

12  „ 

14 

For 

12  X 

10 

15  M 

16 

If  more  than  one  lens  is  required,  I  strongly  advise  the  second  lens 
should  be  a  long-focus  single  or  landscape  lens  of  a  focal  length 
equal  to  i£  times  that  of  the  doublet.  If  a  third  lens  is  required, 
then  a  doublet  of  short  focus  may  be  chosen,  the  focus  being 
about  two-thirds  that  of  the  doublet.  Thus,  for  a  half-plate,  we 
have  first  a  rectilinear  of  9-in.  focus,  then  a  single  lens  of  13^-in. 
and  lastly  a  second  doublet  of  6-in.  focus.  Such  a  set  of  lenses 
will  enable  us  to  obtain  pictures  of  almost  every  character,  and  to 
obtain  the  images  of  objects  varying  in  size.  See  Wide  Angle. 
Many  an  amateur  possessing  a  single  or  landscape  lens,  which 
he  may  have  purchased  at  the  outset  with  his  outfit,  yearns  for  a 
doublet,  in  the  hope  of  improving  his  pictures,  acting  under  the 
very  general  impression  that  far  finer  results  are  given  by  the 
latter  lens.  This,  however,  is  a  mistake.  The  sole  superiority 
of  a  doublet  consists  in  its  working  at  a  larger  aperture,  and  in 
being  free  from  Distortion  {q.v.).  It  may,  perhaps,  be  of  interest 
to  some  if  I  state  that  on  examining  my  register  of  exposures 
for  three  months,  I  find  that  out  of  137  exposures  a  doublet 
was  only  used  twenty-three  times  ;  of  these  in  nineteen  instances 
it  was  for  copying  diagrams,  the  other  four  for  interiors.  There 
is  a  good  deal  of  talk  about  distortion  caused  by  single  lenses, 
but  few  would  be  able  to  detect  the  same  in  my  prints,  many  of 
which  have  buildings  included  in  the  views. 

Testing  a  Lens. — The  first  point  to  decide  in  testing  a  lens  is 
its  equivalent  focus  or  focal  length ;  the  second  point,  the  ratio 
aperture  of  the  diaphragms  ;  the  third,  covering  power  of  the 
lens ;  (4)  the  flatness  of  the  field  ;  (5)  the  freedom  from  spherical 
and  chromatic  aberrations  ;  (6)  the  freedom  from  flare  and  ghosts  ; 
(7)  the  accurate  centreing  of  the  lenses  ;  (8)  the  perfect  polishing 
of  the  surfaces  ;  (9)  the  freedom  from  striae  or  waves. 

(1)  To  Determine  the  Equivalent  Focus. — Several  methods  are 
given  under  this  heading. 

287 


Len] 


DICTIONARY  OF  PHOTOGRAPHY. 


(2)  To  Determine  the  Ratio  Aperture  of  the  Diaphragms. — 
This  is  described  under  Diaphragms  (q.v.). 

(3)  The  Covering  Power  of  the  Lens. — To  determine  the 
covering  power  of  the  lens  is  by  no  means  a  difficult  object, 
especially  if  the  lens  be  used  with  a  given-sized  plate,  that  is  for 
the  one  for  which  it  is  advertised.  Many  lenses  will,  with  small 
diaphragms,  cover  a  much  larger  plate  than  that  for  which  they 
are  designed,  and  all  lenses  will  cover  a  smaller  plate.  If  you 
wish  to  test  whether  a  lens  will  cover  a  given-sized  plate,  all  that 
you  require  to  do  is  to  affix  the  lens  to  the  front  of  a  camera 
which  has  a  focussing  screen  of  the  given  size,  and  then  focus  till 
you  obtain  a  sharp  image  at  the  centre  ;  it  will  be  at  once  seen 
whether  the  lens  will  cover.  But  it  is  not  only  necessary  that  a 
lens  should  cover  a  given-sized  plate,  but  most  photographers 
require  that,  besides  covering  a  plate,  a  lens  should  give  good 
definition  all  over  a  plate,  which  is  a  totally  different  thing. 
Many  a  lens  will  cover  a  plate  and  yet  give  very  poor  definition 
at  the  margins,  because  either  (a)  the  spherical  aberration  for 
oblique  pencils  is  not  corrected,  or  (b)  it  has  a  very  curved  field. 
For  special  purposes  such  as  hand-camera  and  instantaneous 
work  it  is  now  considered  absolutely  necessary  that  a  lens  shall 
give  sharp  definition  over  the  entire  surface  of  the  plate  for 
which  it  is  intended.  It  is  often  suggested  that  to  test  for 
this  in  a  lens  the  best  plan  is  to  set  up  a  sheet  of  newspaper 
and,  focussing  sharply,  to  examine  the  definition  with  a  com- 
pound focusser.  Personally  I  prefer  to  make  a  practical  test 
as  suggested  by  Mr.  W.  E.  Debenham,  as  follows: — In  order 
to  arrive  at  a  judgment  as  to  whether  a  lens  defines  as  sharply 
as  it  should  do,  it  is  necessary  to  have  something  which  re- 
presents the  standard  of  sharpness  expected  from  the  particular 
kind  of  lens.  There  is  no  recognised  standard,  and,  for  want 
of  it,  such  absurd  expressions  as  "  as  sharp  as  a  needle "  have 
sometimes  been  used  to  describe  exceptionally  fine  definition. 
Perhaps  the  Congress  at  Paris  may  settle  upon  something  in  the 
way  of  a  standard  for  the  defining  power  of  lenses.  Meanwhile, 
however,  we  will  describe  the  standard  which  we  have  employed, 
and  which  has  served  to  make  the  work  of  various  lenses  com- 
parable. W e  take  a  sheet  of  printed  matter  that  is  always  to  be 
had  of  one-sized  type  (nonpareil),  namely,  "  Births,  Deaths,  and 
Marriages  "  column  of  the  Standard  newspaper.    This  column  is 

288 


DICTIONARY  OF  PHOTOGRAPHY.  [Len 

placed  slantwise,  the  top  of  the  column  being  farthest  from  the 
plate,  but  each  particular  line  runs  square  across  it  as  before 
directed,  in  the  middle  of  the  column,  and  at  such  a  distance  that, 
when  a  printed  line  is  focussed  in  the  centre  of  the  field,  the 
image  is  one-eighth  of  the  original  size.  The  width  of  two 
columns  in  the  focussing  screen  will  be  just  over  five-eighths  of 
an  inch.  With  a  good  portrait  lens  having  an  aperture  of  one- 
fourth  of  the  focus,  the  standard  adopted  as  unity  by  the  Photo- 
graphic Society  ot  Great  Britain  up  to,  say,  a  12-in.  lens,  at  all 
events,  the  definition  in  the  centre  of  the  field  should  be  such 
that  the  small  type  will,  on  examination  with  an  eye-piece,  be 
quite  legible.  The  same  test  may  be  employed  for  all  lenses, 
and  those  professing  to  be  aplanatic  will  for  the  most  part  be 
found  to  pass  it,  though  with  different  degrees  of  perfection.  Of 
course,  by  stopping  down,  almost  any  lens  may  be  made  to  define 
well,  at  all  events,  in  the  centre  of  the  field  ;  but  we  are  speaking 
of  lenses  worked  with  the  largest  apertures  with  which  they  are 
supplied,  and  which,  in  most  lenses  of  the  Steinheil  aplanatic 
type — rapid  rectilinear,  rapid  symmetrical,  Euryscope,  etc. — will 
be  found  from  fjy  to  f/9.  In  the  newer  forms  of  cemented 
aplanatic  lenses,  in  which  the  glass  from  the  Jena  factory  has 
been  utilised,  somewhat  larger  apertures  have  been  practicable, 
but  whatever  the  aperture  is,  it  is  to  be  supposed  that  good 
definition  is  obtainable  with  it,  and  therefore  the  test  mentioned 
may  be  fairly  employed.  When  we  come  to  examining  the 
defining  power  of  the  lens  at  some  distance  from  the  centre 
of  the  field,  we  shall  find  with  rapid  lenses  that  there  is  a  very 
great  falling  off.  Taking  again  as  an  example  a  portrait  lens  of 
12-in.  focus  and  of  aperture  //4,  and  slewing  round  the  camera 
so  that  the  image  is  rendered  at  a  distance  of  2  in.  from  the  centre 
of  the  focussing  screen,  we  shall  find  that  the  small  type  of  our 
newspaper  column  is  no  longer  readable.  The  larger  type  used  for 
the  heading  "Marriages,"  etc.,  should  still  be  legible,  but  nothing 
more.  Now  insert  diaphragm y/8,  No.  4  on  the  universal  system, 
and  the  small  type  again  becomes  distinguishable.  With  a 
Steinheil  type  lens  of//8  aperture  the  definition  at  this  angle  may 
be  expected  to  be  still  satisfactory  without  further  stopping 
down.  This  then  is  Mr.  Debenham's  method  ;  personally  I  use  a 
modification  of  it,  only  in  that  I  cut  out  several  of  such  columns 
as  he  mentions,  and  paste  them  on  a  piece  of  stout  millboard, 

289  U 


Ldl]  DICTIONARY  OF  PHOTOGRAPHY. 

which  is  framed  to  keep  it  flat.  Diagonally  across  the  centre  is 
pasted  an  ordinary  inch  tape.  The  whole  arrangement  is  then 
hung  up  flat  against  the  wall,  and  the  camera  set  up  and  the 
image  focussed  till  reduced  to  one-eighth  in  size,  as  suggested 
by  Mr.  Debenham.  I  may  remark  here  that  focussing  is  not 
effected  in  the  ordinary  way  on  the  ground-glass  of  the  camera, 
but  on  a  specially  prepared  sheet  of  obscured  glass  inserted  in 
the  dark  slide,  which  is  slid  into  the  grooves  at  the  back  of  the 
camera.  The  specially  prepared  sheet  of  obscured  glass  was 
made  by  me  by  slightly  etching  the  surface  of  a  perfectly  true 
piece  of  thin  plate-glass  by  means  of  hydrofluoric  acid,  and  this 
sheet,  when  looked  through,  shows  merely  a  very  thin  milky 
haze,  which  shows  no  grain,  the  centre  being  marked  by  a  cross 
in  fine  Indian  ink.  Focussing  is  easily  effected  by  means  of  a 
magnifier,  and  the  centre  of  the  screen  is  made  to  coincide  with 
the  central  division  of  the  inch  tape.  The  dark  slide  is  now 
removed,  a  slow  dry  plate  inserted  in  the  dark-room,  an 
exposure  made,  the  plate  developed,  and  the  resulting  nega- 
tive, when  dry,  carefully  examined  by  the  magnifier.  The  image 
of  the  inch  tape  at  once  affords  a  guide  as  to  the  limit  of  sharp 
focus,  and  it  is  therefore  possible  to  state  without  trouble  the 
extent  of  sharp  focus  expressed  in  terms  of  the  focal  length  as 
suggested  by  Mr.  Debenham.  For  example,  a  lens  was  received 
for  examination  which  gave  the  following  data  : — 

Equivalent  focus     ...       ...       ...  in. 

Working  aperture   ...       ...       ...  f/7'9- 

Ratio  aperture  of  largest  diaphragm  //8. 

Limit  of  sharp  focus    fl'%25  =  9'5  in. 

This  lens  would  therefore  cover  any  plate  sharply  the  diagonal 
of  which  was  not  more  than  c,\  in.  In  the  case  of  small  lenses, 
or  lenses  of  short  focus  I  should  say,  I  prefer  a  still  more  practical 
test,  and  that  is  to  focus  sharply,  as  described  above,  on  the 
bricks  of  the  house  opposite  my  first-floor  window,  throwing  the 
window  at  which  I  place  the  camera  open.  Now  these  bricks 
are  just  52  feet  (by  actual  measurement)  from  the  point  at  which 
the  lens  is  placed,  an  exposure  is  made,  and  the  results  examined 
on  the  negative.  This  test  more  nearly  approaches  the  conditions 
of  practical  work. 

(4)  To  Determine  the  Flatness  of  Meld.    The  foregoing  tests 
290 


DICTIONARY  OF   PHOTOGRAPHY.  [Len 

aic  quite  sufficient  to  determine  this,  but  it"  an  actual  illustration 
is  required  of  the  amount  of  the  curvature  of  the  field  we  have 
only  to  use  the  newspaper  again,  and  by  marking  on  the  base- 
board the  focus  for  the  centre,  and  then  refocussing  for  the 
margins,  and  again  marking,  we  can  easily  plot  out  a  curve  which 
shall  show  us  exactly  the  form  of  the  field  of  the  lens. 

(5;  The  Freedom  Jrom  Spherical  and  Chromatic  Aberratio?is. 
The  tests  for  spherical  aberration  are  comparatively  easy  ones. 
A  steady,  naked  flame,  such  as  a  candle  or  small  gas  flame,  may 
be  focussed  sharply  at  the  centre  of  the  screen,  and  the  image 
examined  with  an  eye-piece  ;  it  is  preferable  to  focus  on  a  piece 
of  plain,  not  ground,  glass.  If  a  halo  is  seen  round  the  flame, 
it  may  be  assumed  that  some  spherical  aberration  is  present. 
The  objection  to  this  method  is  that  the  fringes  may  not  be  due 
to  spherical  aberration,  but  to  halation  or  ghosts.  Another  test, 
and  the  one  I  usually  employ,  is  to  fix  to  a  window  two  small, 
dark-coloured  wafers,  with  their  edges  just  in  contact ;  the 
camera  is  set  up  at  least  ten  times  the  focus  of  the  lens  distant, 
and  then  the  images  sharply  focussed  as  stated  above,  with  full 
aperture ;  on  the  insertion  of  a  small  diaphragm  there  should  be 
no  increase  of  sharpness.  Another  method  is  to  proceed  as 
above,  and  affix  to  the  centre  of  the  front  lens  of  a  doublet  or 
the  centre  of  a  single  lens  a  piece  of  black  paper  three-fourths 
of  the  diameter  of  the  lens ;  the  image  which  is  now  formed  by 
the  margins  of  the  lenses  is  sharply  focussed.  The  black  paper 
is  removed,  and  a  small  diaphragm  inserted,  and  the  image  ex- 
amined ;  if  it  requires  refocussing  by  racking  in  or  reducing  the 
distance  between  lens  and  screen,  the  lens  suffers  from  negative 
spherical  aberration  ;  if  the  camera  requires  racking  out,  positive 
spherical  aberration  exists.  Chromatic  aberration,  or  practically 
non-coincidence  of  the  visual  and  actinic  foci,  is  rarely  found  in 
modern  lenses.  No  lens  is  actually  achromatic — i.e.,  without 
colour — because  the  finest  lenses  corrected  as  much  as  is  possible 
(I  except  here  all  lenses  made  with  the  Jena  glass)  show  fring  s 
of  colour,  as  may  be  at  once  practically  proved  by  any  one  in  the 
following  manner : — Arrange  a  thermometer  with  a  naked  bulb, 
so  that  a  spot  of  light  is  reflected  from  the  mercury,  and  focus 
this  spot  of  light  (the  optician's  artificial  star)  on  the  focussing 
screen  of  plain  glass  by  the  aid  of  a  magnifier;  on  racking,  the 
camera  in  slightly,  a  faint  fringe  of  gr^en  is  seen  surrounding  the 

291 


DICTIONARY  OF  PHOTOGRAPHY. 


spot,  and  by  racking  out  beyond  the  focus  a  fringe  of  reddish 
purple  comes  into  view.  This  is  best  seen  with  an  eye-piece. 
To  test,  however,  whether  the  visual  and  actinic  foci  actually 
coincide,  place  the  newspaper  previously  described  squarely 
opposite  the  lens,  but  leaning  away  from  it ;  focus  sharply,  with 
full  aperture,  on  one  particular  line  of  type — focussing  must  be 
effected  by  placing  the  screen  in  the  dark  slide,  or  the  fact  of 
non-coincidence  of  the  plane  of  the  focussing  screen  and  sensitive 
plate  may  cause  error ;  then  on  exposing  a  plate,  if  the  same 
line  of  type  as  focussed  does  not  come  out  the  sharpest,  it  is 
proved  that  the  lens  possesses  a  chemical  focus,  and  we  at 
once  determine  whether  this  is  beyond  or  within  the  visual 
focus. 

(6)  Freedom  from  Flare  and  Ghosts.    Flare  is  visible  as  a 
central  patch  of  light,  and  arises  from  an  incorrect  position  of  the  . 
diaphragm  in  single  lenses,  and  from  reflections  from  the  surfaces 
of  the  lenses  in  doublets.    To  test  for  the  same,  I  use  the  plan 
suggested  by  Mr.  Debenham.    A  sheet  of  black  velvet  or  deep 
red  cloth  is  hung  up  in  a  room  at  night,  and  in  front  of  it,  at 
some  little  distance,  eighteen  to  twenty-four  inches,  is  placed  a 
lighted  candle.    The  image  of  the  flame  is  sharply  focussed,  and 
there  will  be  generally  seen  a  halo  or  ring  of  diffused  light  sur- 
rounding the  flame.    The  camera  is  now  slightly  slewed  round, 
and  the  image  watched ;  if  the  ring  or  halo  of  diffused  light  is 
steady  at  the  centre  of  the  screen,  it  may  be  assumed  to  be 
"flare";  if,  on  the  other  hand,  the  halo  moves  with  the  image 
of  the  flame,  it  is  due  to  a  secondary  image  or  ghost  very  much 
out  of  focus.    To  actually  determine  this,  rack  the  camera  in  or 
out  to  about  half  or  double  the  focal  length,  when  a  small  image 
of  the  flame  will  be  seen  surrounded  by  a  large  disc  of  light,  the 
small  image  being  the  previous  flare,  and  the  halo  the  real  image 
formed  at  the  focus.     "  Ghosts  "  are  the  images  of  a  brightly  lit 
object  reflected  by  the  surfaces  of  the  lens  on  to  another  portion 
of  the  screen.    The  same  may  be  tested  for  as  described  for  flare 
only  ;  the  image  of  the  candle  flame  should  be  brought  to  one 
side  of  the  screen,  and  the  ghosts  looked  for  on  the  opposite 
side.    One  or  more  ghosts  may  make  their  appearance,  and  will 
be  easily  visible  in  this  way.    Practically,  "  ghosts  "  are  a  nuisance 
when  photographing  a  dark  interior  which  contains  a  brilliantly 
lit  window,  as  a  ghost  of  the  window  may  make  its  appearance 

292 


DICTIONARY  OF  PHOTOGRAPHY. 


on  the  opposite  side  of  the  plate  in  a  dark  portion,  and  also  in 
portraiture  a  white  shirt  front  may  appear  duplicated. 

(7)  Accurate  Centreing.  To  test  a  lens  for  accurate  centreing, 
it  is  advisable  to  mount  the  lens  temporarily  in  the  camera  and 
focus  on  a  naked  candle  or  gas  flame  placed  a  little  to  one  side, 
then  turn  back  the  focussing  screen,  and  several  images  of  the 
flame  will  be  seen  on  looking  into  the  camera.  If  the  lens  is 
correctly  centred,  these  images  remain  stationary  when  the  lens 
is  unscrewed  ;  if  they  do  not,  the  lens  should  be  returned  to  the 
maker. 

(8)  Perfect  Polishing  of  the  Surfaces.  This  is  by  no  means 
an  easy  test  for  an  amateur,  but  it  is  possible  to  determine  this 
by  examining  the  surfaces  with  a  very  powerful  eye-piece. 

(9)  Freedom  from  Stria,  or  Waves.  The  presence  or  absence 
of  these  defects  may  be  observed  by  holding  the  lens  near  a 
flame,  when  the  waves,  or  striae,  caused  by  imperfect  admixture 
of  the  glass  material,  may  be  observed. 

Levelling  Slab.  A  perfectly  even  piece  of  glass,  slate,  or  any 
other  material  sufficiently  thick  not  to  bend  when  placed  upon 
the  levelling  stand,  which  is  preferably  of  a  triangular  form, 
having  a  fine  screw  at  each  corner  to  allow  of  the  height  being 
altered  as  required.  The  slab  of  glass,  or  slate,  is  placed  upon 
the  stand,  and  accurately  adjusted  by  means  of  a  spirit-level. 

Lichtdruck.    See  Collotype. 

Light  is  that  principle'  which  emanates  from  all  luminous 
bodies,  and  the  luminosity  of  such  bodies  is  due  to  intensely 
rapid  molecular  vibration,  which  vibration  is  propagated  in  a 
supremely  subtle  elastic  medium,  termed  the  luminiferous  ether, 
and  light  waves  radiate  from  a  body  in  all  directions  and  from 
all  points  of  that  body.  Light  always  travels  in  straight  lines* 
unless  deviated  from  its  course  by  the  action  of  some  body 
through  which  it  passes.  All  substances  are  either  transparent 
(not  hindering  sight),  translucent  (hindering  sight),  or  opaque  : 
transparent  substances  allow  light  to  pass  through  them,  but 
deviate  the  course  of  the  rays  of  light ;  translucent  bodies  whilst 
allowing  some  rays  of  light  to  pass  through  reflect  others ;  whilst 
opaque  bodies  reflect  some  rays  and  absorb  others,  but  the  rays 
passing  on  each  side  of  the  opaque  substance  still  continue  their 
course,  and  leave  behind  the  body  a  space  which  is  not  iilu- 

293 


DICTIONARY  OF  PHOTOGRAPHY. 


minated,  or  only  partially  so.  This  space  is  termed  shadow. 
Shadows,  however,  are  not  rigidly  defined,  as  the  shadow  cast  by 
the  interception  of  rays  from  the  top  edge  are  partly  illuminated 
by  the  rays  from  the  lower  edge,  and  vice  versa,  and  the  shadow 
is  always  partly  illuminated  by  neighbouring  rays.  The  velocity 
of  light  is  about  186,830  miles  per  second.  The  intensity  of  the 
light  varies  in  inverse  proportion  to  the  square  of  the  distance 
from  the  source  of  light.  If  rays  of  light  fall  upon  a  body  which 
is  opaque,  and  the  surface  of  which  is  unpolished,  certain  portions 
of  such  light  will  be  absorbed  or  enter  to  a  certain  depth,  the 
remaining  portion  being  reflected  in  all  directions ;  but  certain 
bodies  absorb  only  certain  of  the  constituent  rays  of  light,  and 
reflect  one  or  more  of  the  others,  and  thus  we  arrive  at  the 
colours  of  objects.  For  example,  an  object  which  absorbs  all  the 
primary  colours  but  red  will  appear  red ;  one  that  absorbs  all 
colours,  black ;  and  one  that  absorbs  none,  white  ;  and  so  on.  A 
ray  of  light  is  reflected  from  a  polished  surface  at  the  same  angle 
with  a  line  drawn  perpendicular  to  the  surface  of  mirror,  that  the 
ray  striking  the  mirror  makes — i.e.,  "the  angle  of  incidence  is 
equal  to  the  angle  of  reflection."  When  a  ray  of  light  strikes  a 
plane  reflecting  surface,  it  will,  after  reflection,  so  diverge  from  a 
point  situated  similarly  behind  the  mirror — i.e.,  the  image  of  an 
object  10  ft.  away  from  the  mirror  will  be  reflected  from  a  point 
seemingly  10  ft.  behind  the  mirror.  When  light  passes  from  one 
transparent  medium  to  another  transparent  medium,  unless  per- 
pendicular to  the  surfaces  of  both,  it  is  refracted  or  bent  aside 
to  a  greater  or  less  degree.  This  power  of  refraction  differs  for 
every  different  substance,  but  remains  the  same  at  all  times  for 
the  same  substance.  It  is  only  at  the  surfaces  of  transparent 
media  that  refraction  occurs.  The  power  of  refraction  possessed 
by  each  body  is  termed  its  "  index  of  refraction."  A  ray  of  light 
refracted  through  a  medium  with  parallel  surfaces  will  have  the 
same  direction  after  leaving  such  medium  as  when  entering  ; 
and  a  ray  of  light  traversing  two  media  having  parallel  external 
surfaces,  but  differing  refracting  indices,  will  emerge  in  a  direction 
parallel  to  the  incident  ray.  When  a  ray  of  light  is  refracted,  it  also 
suffers  what  is  termed  dispersion — i.e.,  it  is  separated  into  its  con- 
stituent rays.  (See  Decomposition  of  Light  and  the  Spectrum.) 


Light-Fog.    See  Fog. 

294 


DICTIONARY  OF  PHOTOGRAPHY. 


[Lin 


Lime,  Chloride  of  (Ger.,  Chlorkalk ;  Fr.,  Chlorure  de  chaux; 
Ital.,  Cloruro  di  calce).  Synonyms  :  Chlorinated  Lime,  Bleaching 
Lime,  Bleaching  Powder,  Hypochlorite  of  Lime.  The  composition 
of  this  is  a  moot  point :  it  is  said  to  be  by  some  a  mixture  of 
calcium  hypochlorite  Ca(C10)2  and  calcium  oxychloride  Ca302Cl2, 
according  to  another  view  its  formula  should  be  CaCl„  CaHClO.,. 
It  is  made  by  passing  chlorine  over  slaked  lime.  It  occurs 
as  a  dirty  white  powder,  generally  moist  if  kept  some  time, 
and  probably  contains  some  undecomposed  hydrate  and  some 
carbonate.  •  When  mixed  with  water  it  forms  a  solution  of 
calcium  hypochlorite  Ca(C10)2  and  calcium  chloride  CaCL,  with 
some  hydrate  Ca(HO)->  and  carbonate  which  remains  to  a  great 
extent  undissolved ;  this  solution  very  readily  parts  with  its 
chlorine,  and  may  be  used  for  preparing  this  gas.  Good  samples 
of  chloride  of  lime  should  contain  30  per  cent,  of  chlorine  which 
is  evolved  on  the  addition  of  an  acid.  It  is  used  as  its  name 
implies  for  bleaching  and  also  for  toning  and  the  preparation  of 
a  hypo-eliminator. 

Lime  Light.   See  Oxyhydrogen  Light. 

Lime  Water.  This  is  a  solution  of  hydrate  of  lime  made  by 
agitating  slaked  lime  (Ca2HO)  with  water.  It  is  but  a  feeble 
alkali,  and  contains  only  \  grain  of  lime  (CaO)  to  the  ounce  of 
water.  By  heating,  this  quantity  is  still  further  reduced.  A 
more  powerful  preparation,  actually  about  fourteen  times  stronger, 
may  be  made  by  triturating  one  part  of  lime  with  twice  its 
weight  of  pure  sugar,  manna,  or  glycerine ;  then  adding  20  parts 
of  water  and  decanting  the  clear  solution.  Lime  water  has  been 
suggested  as  an  accelerator  for  quinol  development ;  but  it  is 
unsuitable,  the  action  being  very  slow.  It  is  also  added  to  some 
toning  baths,  but  seems  to  have  but  little,  if  any,  beneficial 
effect. 

Line  Drawings,  To  Copy.  This  is  a  subject  about  which 
many  difficulties  seem  to  hang,  although  actually  there  is  do 
necessity  for  the  same.  The  chief  point  is  to  use  a  slow  plate, 
one  not  showing  more  than  12  on  Warnerke's  sensitometer  ;  and 
this  must  be  considered  the  limit — one  even  less  sensitive  than 
this  should  be  chosen  ;  the  commercial  lantern  plates  are  usually 
of  this  class.  The  following  directions  will,  it  is  hoped,  make 
this  an  easy  operation  for  any  one.    Having  decided  upon  the 

295 


Lit] 


DICTIONARY  OF  PHOTOGRAPHY. 


size  that  the  resulting  negative  shall  be,  the  next  question  is  to 
determine  the  focus  of  the  lens  to  be  used.    If  only  one  lens  is 
possessed,  then  the  size  of  the  image  is  ruled  by  this,  and  the 
extension  of  the  camera.    Supposing  we  desire  to  reduce  a  plan 
or  line  drawing  from  9X7  in.,  to  4^  x  3^,  the  lineal  reduction 
is  practically  two  ;  therefore  by  consulting  the  table  given  in  the 
Appendix,  we  shall  find  with  a  5-in.  focus  lens  that  our  lens 
must  be  15  in.  from  the  plan  and  j\  in.  from  the  focussing 
screen.     Supposing  our  camera  does  not  rack  out  sufficiently 
far,  we  must  improvise  an  extension  by  means  of  a  3-in.  or  4-in. 
cone,  or  else  by  adapting  one  of  the  cardboard  cases  used  for 
sensitised  paper.    If  we  have  a  choice  of  lenses,  we  may  pick 
that  one  which  is  of  sufficiently  short  focus  to  enable  us  to  use 
the  camera  without  any  additional  extension.    The  next  point  is 
to  place  the  axis  of  the  lens  exactly  central  with  the  print,  and 
the  focussing  absolutely  parallel  with  the  plane  of  the  line 
drawing.    It  is  hardly  necessary  to  dilate  upon  this,  as  any  tyro 
can  do  it.    Then  comes  the  question  of  lighting.    This  should 
be  as  bright  as  possible  ;  the  author,  using  sunlight  diffused  by 
ground  glass,  or  tissue  paper,  when  sunlight  is  to  be  had.  The 
lens  should  be  used  with  a  large  aperture,  so  as  to  get  as  great 
a  contrast  as  possible,  as  the  use  of  small  diaphragms  tends  to 
render  any  picture  or  scene,  and  therefore  any  image  of  a  line 
drawing,  flat  and  wanting  in  contrast.    A  short  exposure  should 
be  given,  if  anything  under-exposure,  because  we  want  to  get 
hardness  and  contrast.    No  guide  can  be  given  for  exposure,  as  it 
depends  so  entirely  upon  the  actinic  power  of  the  light.  The 
developer  should  be  either  quinol,  or  Edwards's  pyro  rede- 
veloper  may  be  used  ;   we  prefer  the  former.  Development 
should  be  continued  as  far  as  possible  without  any  blocking 
of  the   lines  showing;  if  this  shows,  immediately  stop  the 
development,  wash,  and  fix.     After  thoroughly  washing,  the 
negative  should  be  cleared  till  the   lines  show  as  absolute 
bare   glass,  with   the  ground  absolutely  opaque.    For  this 
purpose  we  specially  recommend  Edwards's  clearing  solution 
(p.  80),  used  with  the  iron.    Then,  after  thoroughly  washing, 
if  not  dense  enough,  intensify  with  intensifier  No.  V.,  p.  253). 

Lithium  (Ger.,  Lithium;  Fr.,  Lithium;  Ital.,  Litio).  Li  =  7. 
A  comparatively  rare  metal  occurring  in  lepidolite,  lithia-mica, 

206 


DICTIONARY  OF  PHOTOGRAPHY. 


[Lun 


petalite,  and  triphane.  It  can  be  obtained  by  decomposing 
lithium  chloride  by  a  galvanic  current.  It  is  a  soft  silvery-white 
metal  decomposed  by  water,  and  is  remarkable  as  the  lightest 
solid  element  (Sp.  Gr.  0-59). 

Lithium  Bromide  (Ger.,  Bro?nlithtu?n)  Lithiumbro7nid ;  Fr., 
Bromure  de  lithine ;  Ital.,  Bromuro  di  litio?)  LiBr  =  87.  This 
salt,  which  occurs  in  transparent  white  tablets  or  colourless 
needles  which  are  very  deliquescent,  can  be  prepared  by  direct 
combination  between  the  elements,  or  by  double  decomposition 
of  lithium  sulphate  and  barium  bromide.  Solubility  143  per  cent, 
in  cold,  290  per  cent,  in  hot,  water.  Very  soluble  in  alcohol  and 
ether.    Sometimes  used  in  collodion  emulsion  making. 

Lithium  Chloride  (Ger.,  Chlorlithium,  Lithiumchlorid ;  Fr., 
Chlorure  de  lithine ;  Ital.,  Cloruro  di  litio).  LiCl,2H.,0  =  78-5. 
This  can  be  prepared  in  a  similar  manner  to  the  bromide  salt. 
It  occurs  in  octahedral  crystals  which  are  very  deliquescent. 
Solubility  82  per  cent,  in  cold,  146  per  cent,  in  hot  water,  soluble 
in  alcohol  and  ether.  It  is  used  in  the  preparation  of  collodio- 
chloride  emulsions. 

Lithium  Iodide  (Ger.,  Iodlithium,  Lithiumiodid ;  Fr.,  Iodurc 
de  lithine  ;  Ital.,  Ioduro  di  litio).  Lil  =  134.  Made  in  a  similar 
manner  to  the  bromide  salt.  Occurs  in  yellowish  crystals  which 
are  very  deliquescent.  Solubility,  100  per  cent,  in  cold,  133  per 
cent,  in  hot  water ;  freely  soluble  in  alcohol.  Used  for  iodising 
collodion. 

Litmus  (Ger.,  Lackmus ;  Fr.,  Tournesol ;  Ital.,  Tomasole). 
A  blue  colouring  matter  obtained  from  several  weeds  and  lichens 
by  fermentation  with  potash  and  ammonia.  It  appears  com- 
mercially as  small  cakes,  being  made  into  a  mass  with  chalk. 
It  is  used  to  indicate  the  presence  of  an  alkali  or  an  acid,  the 
latter  turning  the  solution  red,  and  alkalies  restoring  the  colour; 
the  indications,  however,  are  not  very  reliable.  It  is  usually  met 
with  in  the  form  of  small  books  made  by  steeping  unsized  paper 
in  tincture  of  litmus. 

Liver  of  Sulphur.    See  Potassium  Sulphide. 
Loss  of  Tone  in  Fixing.   See  Toning. 
IdUnar  Caustic.    See  Silver  Nitrate. 

297 


Lux] 


DICTIONARY  OF  PHOTOGRAPHY. 


Luxograph.  A  term  used  to  denote  certain  methods  of 
artificial  lighting. 

Macro -Photography.  A  term  used  to  denote  the  enlarge- 
ment of  the  negative. 

Magic-Lantern.  An  apparatus  used  to  project  a  magnified 
image  of  a  positive  upon  a  white  screen  in  a  darkened  room. 
Practically  it  consists  of  a  tin  box,  in  which  is  placed  a  lamp  in 
the  focus  of  a  silvered  reflector,  the  light  being  condensed  by  a 
pair  of  plano-convex  lenses,  the  positive  being  placed  close 
to  the  condensers,  and  a  special  photographic  lens  being  placed 
at  the  focus  of  the  condensing  lens,  which  produces  a  magnified 
image.  Usually  a  three-  or  four-wick  lamp  is  employed  to  give 
the  illumination,  the  edges  of  the  flames  being  presented  to  the 
condensers,  which  should  be  as  close  as  possible  to  the  flame 
without  danger  of  cracking  them.  The  positive  should  be  placed 
upside-down,  and  film-side  inwards,  as  close  as  possible  to  the 
condensers ;  the  magnifying  lens,  which  is  usually  provided  with 
a  rackwork  movement  to  ensure  easy  and  accurate  focus,  being 
placed  at  the  focus  of  condensers.  The  following  rules  and  table 
will  be  found  useful  in  determining  the  dimensions  of  the  pictures 
thrown  on  the  screen  with  various  lenses  : — 

1.  Knowing  the  length  of  room  and  diameter  of  picture  desired, 
required  to  find  the  focus  of  front  objective  of  lantern.  Multiply 
the  distance  between  the  lantern  and  screen  by  the  size  of  the 
opening  in  slide,  and  divide  by  the  diameter  of  disc. 

Example.  Room  length  50  feet,  diameter  of  picture  20  feet ; 
required  to  know  focus  of  lens  to  be  used.  (Three  inches  is 
always  taken  as  the  size  of  opening  of  slide.) 

5°  x  3_  i5o  _  71-in.  focus  lens. 
20         20  2 

2.  Having  a  given  focus  lens,  and  given  diameter  of  picture, 
required  to  know  what  distance  from  screen  to  place  lantern. 
Multiply  the  diameter  of  picture  required  by  the  focus  of  the 
lens,  and  divide  by  the  diameter  of  the  slide. 

Example.  Size  of  picture  desired  15  feet;  focus  of  lens 
8  ins. 

15  *  8=       -  4o  feet, 
3 

298 


DICTIONARY  OF  PHOTOGRAPHY. 


[Mag 


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3 


299 


Mag]  DICTIONARY  OF  PHOTOGRAPHY. 

3.  Having  a  given  focus  lens,  and  given  distance  between 
lantern  and  screen,  required  to  know  diameter  of  picture  that  will 
be  produced.  Multiply  the  distance  between  lantern  and  screen 
by  the  opening  of  the  slide,  and  divide  by  the  focus  of  the  lens. 

Example,  Lens  of  9-in.  focus,  distance  between  lantern  and 
screen  40  feet,  required  size  of  disc. 

4°  X  3=  HP  =  13  ft.  4  in.  diameter  of  disc. 
9 

Magic  Pictures.  A  process  discovered  by  Sir  John  Herschel, 
which  is  more  of  an  ingenious  toy  than  of  any  practical  use. 
The  process  is  as  follows  : — Print  as  usual  on  albumenised 
paper,  fix  without  toning,  and  wash  thoroughly ;  immerse  the 
prints  in  a  saturated  solution  of  perchloride  of  mercury  until  the 
image  is  thoroughly  bleached  and  disappears,  wash  and  dry. 
To  make  these  invisible  images  appear  at  the  word  of  command, 
as  if  by  magic,  place  over  them  a  wetted  sheet  of  blotting  paper, 
which  has  been  previously  soaked  in  a  saturated  solution  of 
hyposulphite  of  soda,  and  pass  the  hand  over  them,  when  the 
image  will  start  up  with  more  than  its  original  vigour. 

Maglip,  or  Meglip.  An  artist's  material,  made  by  mixing 
boiled  linseed  oil  with  mastic  varnish.  It  is  used  for  thinning 
oil  colours  and  for  glazing  on  delicate  tints  on  finished  oil- 
paintings. 

Magnesium  (Ger.,  Magnesium;  Fr.,  Magnesium-;  Ital., 
Magnesid).  Mg_24.  Occurs  in  large  quantities  as  dolomite 
or  mountain  limestone — an  impure  carbonate.  The  metal  is 
silvery  white  in  colour,  and  is  met  with  commercially  in  the  form 
of  wire,  ribbon,  and  powder.  It  is  now  of  common  use  for  pro- 
ducing negatives  by  night,  as  the  metal  burns  at  a  comparatively 
low  temperature,  giving  an  extremely  actinic  and  brilliant  light. 
It  has  also  been  suggested  as  a  means  of  precipitating  silver  from 
old  fixing  baths  (see  Kesidues). 

Magnesium  Chloride  (Ger.,  Chlormagnesium ;  Fr.,  Chlorure 
de  magnesium  ;  Ital.,  Cloruro  di  magnesid).  MgCl2,6H20  =  203. 
White  crystals  or  needles,  very  deliquescent,  formed  by  the 
action  of  chlorine  on  magnesium,  or  by  dissolving  magnesia  or 
magnesium  carbonate  in  hydrochloric  acid.    It  has  been  employed 

300 


DICTIONARY  OF  PHOTOGRAPHY. 


Mas] 


in  gelatino-chloride  emulsions,  and  was  proposed  by  Liesegang 
as  a  Fixing  Agent.  Solubility  :  160  per  cent,  in  cold,  370  per 
cent,  in  boiling  water ;  50  per  cent,  in  absolute  alcohol ;  500  per 
cent,  in  boiling  alcohol. 

Magnesium  Sulphate  (Ger.,  Magnesittmsidphat,  Schwefel- 
sdures  Magnesium  ;  Fr.,  Stdfate  de  magnesie  ;  Ital.,  Solfato  di 
magnesia).  Synonyms :  Sulphate  of  Magnesia,  Epsom  Salts. 
MgS047H20.  Occurs  naturally  in  certain  springs,  but  is  usually 
made  by  dissolving  dolomite  in  dilute  sulphuric  acid,  and  subse- 
quent purification  and  crystallisation.  It  has  been  recommended 
as  a  preventative  of  frilling.  Solubility  :  104  per  cent  in  cold, 
and  700  per  cent  in  hot  water;  insoluble  in  alcohol. 

Manganese,  Bin-oxide  of  (Ger.,  Mangandioxyd,  Braunstein  ; 
Fr.,  Peroxyde  de  manganese ;  Ital.,  Perossido  di  manganese). 
Mn02=86.  Synonyms:  Manganese  Dioxide,  Black  Oxide  of 
Manganese.  Occurs  native  as  the  ore  of  manganese  as  a  black 
crystalline  powder,  and  is  used  for  the  home  production  of  oxygen 
for  the  limelight. 

Manipulation.  A  term  used  to  express  the  conduct  of  any 
photographic  operation  or  process. 

Masking  Skies.   See  Printing. 

Masks  and  Discs.  Pieces  of  opaque  paper  used  in  photo- 
graphic printing,  usually  with  albumenised  paper.  In  the  opaque 
paper  shaped  openings  are  cut ;  and  the  piece  cut  out  is  termed 
the  disc,  the  margin  being  called  the  mask.  The  mask  is  placed 
between  the  negative  and  the  paper,  when  it  is  obvious  a  print 
will  result  of  the  form  given  by  the  opening  of  the  mask,  and  the 
margin  where  covered  by  the  mask  will  be  white.  The  print 
may  be  finished  off  at  this  stage,  or  the  disc  may  be  carefully 
and  accurately  placed  over  the  print,  and  the  margins  exposed 
to  light  till  they  darken  to  the  required  tint.  A  good  effect  is 
sometimes  given  to  portraits  with  light  backgrounds  by  printing 
under  a  mask,  then  using  a  disc  and  blackening  the  margin, 
enamelling  the  print,  and  giving  the  centre  portion  a  convexity, 
as  described  under  Cameo. 

Mastic,  or  Mastich.  A  resinous  exudation  from  the  stems 
of  Pistacia  lentisctis,  grown  in  the  island  of  Scio.  It  is  usually 
met  with  in  the  form  of  whitish  or  yellowish-white  drops  or 

301 


Mat] 


DICTIONARY  OF  PHOTOGRAPHY. 


tears,  about  the  size  of  small  peas.  Insoluble  in  water  ;  almost 
entirely  soluble  in  alcohol,  ether,  chloroform,  oil  of  turpentine, 
and  benzole.    It  is  used  for  preparing  certain  Varnishes  (q.v.). 

Matt  Paper.  Popular  opinion,  amongst  photographers  at 
least,  has  veered  round  towards  printing  papers  with  a  dull  or 
non-glossy  surface.  Several  commercial  makes  of  matt-surface 
gelatino-chloride  paper  have  been  placed  on  the  market  which 
require  no  different  treatment  to  the  ordinary  glossy  paper. 

Matt  Surface.  A  dull,  not  glossy  or  shiny,  surface  obtained 
in  various  ways  according  to  the  material — glass,  metal,  paper,  etc. 

Matt  Varnish.    See  Varnish. 

Mealiness  Of  Prints.  A  peculiar  mottled  appearance  on  the 
surface  of  prints,  due  to  a  weak  paper-sensitising  bath ;  and  as 
this  is  also  the  cause  of  lack  of  vigour,  contrast,  and  brilliancy, 
the  term  is  frequently  used  to  denote  all  these. 

Measles.  A  peculiar  defect  in  prints,  which  shows,  when  they 
are  held  up  to  the  light,  as  opaque  blotches,  which  are  due  to 
imperfect  fixation  and  non-solution  of  the  insoluble  hypo-sulphite 
of  silver.  On  keeping,  these  spots  turn  yellow,  due  to  formation 
of  sulphide  of  silver ;  whence  the  name,  from  a  fancied  re- 
semblance to  the  human  ailment. 

Measures.    See  Weights  and  Measures. 

Meniscus.    See  Lens. 

Mercuric  Chloride  (Ger.,  Quecksilberchlorid,  Mercurichlorid, 
Sublimat ;  Fr„  Bichlorure  de  mercure ;  Ital.,  Bicloruro  di  mer- 
curid).  HgCl2  =  27i.  Synonyms:  Perchloride  of  Mercury,  Bi- 
chloride of  Mercury,  Corrosive  Sublimate,  Sublimate,  Muriate  of 
Quicksilver.  Can  be  prepared  by  heating  mercury  in  an  excess 
of  chlorine,  but  it  is  prepared  commercially  by  sublimation  from 
a  mixture  of  mercuric  sulphate  and  common  salt.  It  is  usually 
met  with  in  commerce  in  extremely  heavy  colourless  prismatic 
crystals  or  as  a  white  powder.  Specific  gravity  :  5*43.  Solubility  : 
1  in  19  of  cold,  1  in  3  of  hot  water,  1  in  5  ol  rectified  spirit,  1  in 
6  of  ether.  It  sublimes  without  decomposition,  and  melts  at 
5090  F.  It  is  used  for  Intensification  {q.v.).  Its  solution  in 
water  is  liable  to  decomposition  ;  but  any  soluble  chloride  pre- 
vents this,  and  nearly  all  chlorides  increase  its  solubility  in  cold 

302 


DICTIONARY  OF  PHOTOGRAPHY. 


[Min 


water,  a  compound  salt  being  formed.  It  is  a  most  powerful 
poison,  3  grs.  being  the  smallest  fatal  dose  known.  The  antidote 
is  albumen,  or  white  of  egg,  with  which  its  forms  an  insoluble 
compound,  followed  by  emetics.  As  the  salt  is  readily  absorbed 
by  the  skin,  it  is  advisable  not  to  dabble  unnecessarily  in  it. 

Mercury  (Ger.,  Quecksilber ;  Fr.,  Mercure;  Ital.,  Mercurio). 
Hg  =  200.  Synonym:  Quicksilver.  Occurs  native,  but  is  chiefly 
\  obtained  by  roasting  the  ore  cinnabar,  which  is  an  impure  sul- 
phide, obtained  from  China,  Spain,  California,  and  America. 
Mercury,  at  ordinary  temperatures,  is  a  brilliant  silvery  white 
metallic  liquid,  becoming  solid  at  -400  F.,  and  volatilising  below 
the  heat  of  visible  redness.  Specific  gravity:  13-5.  It  has  now 
but  little  photographic  interest,  but  was  used  in  the  old  daguerreo- 
type days  to  develop  the  image. 

Metallic  Spots.  These  sometimes  occur  on  albumenised 
paper,  and  are  due  to  impurities,  usually  metallic  iron,  in  the 
substance  of  the  paper  itself. 

Methylated  Ether.   See  Ether. 

Metric  System.   See  Weights  and  Measures. 

Micro-Photography — the  antithesis  of  macro-photography- - 
consists  of  the  reproduction  of  positives  in  a  very  minute  size, 
which  require  the  use  of  a  simple  microscope  or  magnifying  glass 
to  examine.  It  must  not  be  confounded  with  photo-micrography, 
which  is  the  production  of  photographs  of  microscopic  objects  ; 
yet,  curiously  enough,  in  Hardwich's  "  Photographic  Chemistry," 
ninth  edition,  Photo-micrography  is  described  under  Micro- 
photography.  Micro-photographs  are  well  known  to  the  majority 
of  amateurs,  from  the  minute  photographs  which  are  usually 
sold  at  seaside  places,  the  photographs  being  fixed  behind  a 
minute  magnifying  glass  in  the  handle  of  some  little  but  fancy 
article.  Their  production  is  comparatively  easy,  but  the  collodion 
process  is  the  only  one  possible  to  use.  It  is  obvious  that  it  is 
nothing  but  the  process  of  reduction  carried  out  to  a  minute 
degree  ;  but  as  the  focussing  of  so  small  a  point  is  impossible, 
some  large  object  must  be  photographed  and  the  negative  put  in 
its  place. 

Minim.    See  Weights  and  Measures. 

303 


Mir]  DICTIONARY  0^  PHOTOGRAPHY. 


Mirror,  Reversing.  One  of  the  essentials  for  carbon  and 
all  line  work,  unless  film  negatives  are  used  (see  Reversed 
Negatives). 

Mirror  Silvering.  As  an  amateur  may  desire  to  resilver  a 
mirror  or  a  copper  reflector,  the  following  recipes  may  be  found 
useful : — 


For  glass- 


No.  i. 


Nitrate  of  silver 
Distilled  water 


No.  2. 


Nitrate  of  ammonia... 
Distilled  water 


175  grs.  or  10  grms. 
10  ozs.  „  250  c.cm. 

262  grs.  or  15  grms. 
10  ozs.  ,,  250  c.cm. 


No.  3. 

Pure  caustic  potash   437 '5  grs.  or  25  grms. 

Distilled  water       ...       ...       10  ozs.     250  c.cm. 


No.  4. 


Pure  sugar-candy 
Distilled  water 


210  grs.  or     6  grms. 
5  ozs.      125  c.cm. 


Dissolve  and  add 


Tartartic  acid    50  grs.  or     3  grms. 

Boil  in  a  flask  for  ten  minutes,  and  when  cool  add 


Alcohol 

Distilled  water  to 


1  oz.  or  25  c.cm. 
10  ozs.  „  250  „ 


For  use  :  Mix  Nos.  1  and  2  in  equal  parts  ;  mix  Nos.  3  and  4  in 
equal  parts ;  then  mix  the  two  solutions,  and  suspend  the  glass  in  it. 
To  silver  copper  or  any  metal  it  must  first  of  all  be  cleansed  with 
dilute  acid  to  free  from  dirt,  etc.,  then  well  washed,  and  one  of 
the  following  applied : — Dissolve  60  grs.  of  nitrate  of  silver  in 
1  oz.  of  distilled  water ;  add  sufficient  liq.  ammonia  to  redissolve 
the  precipitate  first  formed  ;  add  to  this  solution  ^  drm.  of  caustic 
potash  solution  and  ^  drm.  of  glycerine  ;  apply  to  the  metal ;  add 
a  few  drops  of  ether  ;  rub  with  a  tuft  of  cotton-wool ;  dry  before 
the  fire,  and  polish  ;  repeat  as  often  as  desired  to  brighten  it. 

304 


DICTIONARY  OF  PHOTOGRAPHY. 


[Mou 


Or 

Nitrate  of  silver 
Liq.  ammonia 
Hyposulphite  of  soda 
Prepared  chalk 
Distilled  water 


65  grs.     or   3-5  grms. 

60  mins.  „    7  6  c.cm. 
100  grs.  6*4  grms. 

100    „       „    6-4  „ 
1,000    „       „  667  c.cm. 


Mix,  and  apply  with  a  flannel.  Or 

Nitrate  of  silver    60  grs.  or  4  grms. 

Cream  of  tartar       ...       ...  120  8  ,, 

Salt   120  ,,    ,,  8 

Cyanide  of  potash   60  „  ,,6 

Make  into  paste  with  water  and  chalk,  and  apply  with  a  flannel. 

Monocle.  Under  this  term  have  been  introduced  uncorrected 
spectacle  lenses,  which  have  been  strongly  recommended  for 
portraiture  and  ordinary  landscape  work  where  softness  of  defini- 
tion is  desired.  The  usual  form  of  lens  employed  is  the  peri- 
scopic  of  about  i^-in.  diameter,  and  may  be  obtained  of  any 
focus  from  about  2-in.  and  upwards.  These  lenses,  being  un- 
corrected, necessarily  have  two  foci,  a  chemical  and  visual,  and 
it  is  therefore  necessary  to  make  a  correction  after  focussing  and 
before  exposing.  For  ordinary  landscape  work  the  necessary 
correction  may  be  made  by  means  of  the  formula  A/=:/°'°2> 
which  is  practically  equal  to  7Vth  of  the  focus.  But  this  only 
applies  when  the  lens  is  working  at  its  equivalent  focus.  In 
the  Appendix  will  be  found  tables  giving  the  necessary  correction 
for  varying  foci  and  sizes  of  images. 

Monocular  Vision.  As  the  term  implies,  it  is  seeing  with 
one  eye  only.  It  was  formerly  supposed  by  many  eminent 
opticians  and  physicists  that  one  eye  only  was  employed  in 
vision  ;  but  Wheatsone,  to  whom  the  great  invention  of  the 
principle  of  the  stereoscope  was  due,  proved  the  fallacy  of  this. 
In  monocular  vision  objects  on  the  true  optical  axis  line  are 
distinctly  seen,  but  other  objects  less  so,  although  they  are  in  the 
circle  of  vision,  and  in  this  particular  the  similarity  of  the  lens 
and  the  human  eye  is  very  evident.  Monocular  vision  can  judge 
the  direction,  but  not  the  distance  of  an  object. 

Mountant.  The  substance  used  to  make  the  print  adhere  to 
its  mounts.    It  is  absolutely  necessary  that  the  mountant  should 

305  X 


DICTIONARY  OF  PHOTOGRAPHY. 


be  free  from  acidity,  in  order  to  prevent  the  destruction  of  the 
delicate  image.  There  are  several  kinds  in  common  use — viz., 
starch  paste,  arrowroot,  gum,  dextrine,  india-rubber  solution, 
liquid  glue,  and  gelatine. 

Starch  Mountant  Starch  in  powder  i  oz.  ;  mix  into  a  cream 
with  I  oz.  of  water,  and  add  to  it,  constantly  stirring,  8^  ozs.  of 
boiling  water  in  which  20  grs.  of  common  alum  and  5  drops  of 
carbolic  acid  have  been  dissolved.  The  mixture  should  be  now 
a  clear  translucent  jelly  free  from  lumps  ;  if  it  is  not,  it  should 
be  gently  heated  in  a  dish  or  pan  till  it  clears,  constant  stirring 
being  an  absolute  necessity  ;  then  it  should  be  squeezed  through 
fine  muslin.  Ordinary  household  flour  makes  a  more  adhesive 
paste,  but  is  more  liable  to  acidity.  Both  will  keep  fit  for  use 
about  a  week,  after  which  they  should  be  rejected. 

Arrowroot  Mountant,  called  Permanent  Paste.  Dissolve  by 
the  aid  of  gentle  heat 

Arrowroot    ...    150  grs.  or   10  grms. 

Gelatine      ...       ...       ...    150  „     ,,     10  ,, 

Distilled  water    3  ozs.  ,,   100  c.cm. 

When  cool,  add 

Methylated  spirit    ...       ...      2^  drms.  or  9  c.cm. 

Carbolic  acid    3  drops  „  0-3  ,, 

Gum  Solution,  or  Mucilage.  Pale-coloured  gum  arabic  in 
clean  lumps,  4  ozs.  ;  distilled  water,  8  ozs.  Wash  the  gum  by 
placing  it  in  a  half-pint  cup  or  measure  ;  add  half-pint  of  water  ; 
stir  briskly  round  twice  or  three  times,  and  pour  off  the  water : 
this  carries  off  any  dust  or  mechanical  impurities.  Now  add 
the  distilled  water,  and  stir  frequently  at  intervals  till  dissolved. 
It  should  be  kept  in  bottles  filled  as  full  as  possible,  and  the 
addition  of  a  little  carbolic  or  salicylic  acid  will  help  to  preserve 
it.  It  will  keep  only  about  ten  or  fourteen  days,  and  when  made 
with  hot  water  about  half  that  time.  Powdered  gum  arabic 
should  never  be  used. 

Dextrine  Solution.  This  is  one  of  the  nastiest  of  all  mountants, 
and  decidedly  unsatisfactory.    It  can  be  made  as  follows  : — 

Pure  white  dextrine  ...       1  oz.    or   28  grms. 

Boiling  distilled  water      ...       3  ozs.  ,,  100  c.cm. 

Methylated  spirit    ...       ...       £  oz.    ,,     14  „ 

Stir  till  dissolved,  and  strain  through  calico. 

306 


DICTIONARY  OF  PHOTOGRAPHY. 


[Mou 


India-rubber  Solution 

Pure  masticated  rubber     ...      80  grs.    or  0-5  grm. 
Chloroform  or  benzole      ...       8  ozs.    „     25  c.cm. 

Shake  till  dissolved.  Benzole  is  cheaper  than  chloroform,  but 
the  smell  is  rather  unpleasant. 

Gelatine.  This  is  the  author's  favourite  mountant.  It  is  less 
liable  to  change  than  any  other  medium,  and  if  properly  made  is 
more  convenient  and  easier  of  application.  The  print  can  be 
mounted  whilst  still  damp,  and  it  can  be  shifted  about  on  the 
mount,  or  any  excess  of  mountant  wiped  off,  without  leaving 
any  trace  on  the  mount,  even  the  highly  enamelled  ones.  The 
following  is  the  most  satisfactory  method  that  the  author  has 
found: — Soft  gelatine,  200  grs. :  soak  in  distilled  water  (6  ozs.) 
for  an  hour.  Dissolve  by  the  aid  of  a  water  bath,  and  add,  in 
small  quantities  at  a  time,  methylated  spirit,  2\  ozs.,  stirring  con- 
stantly ;  allow  it  to  set.  Should  any  spirit  separate  out,  it  should 
be  remelted,  and  a  little  more  water  added.  The  product  should 
be  a  pure  milk-white  firm  jelly.  A  little  carbolic  acid  may  be 
added  if  desired.  When  required 'for  use,  melt  by  the  aid  of  hot 
water  or  a  water  bath. 

Liquid  Glue.  This  is  sometimes  used,  but  as  many  different 
preparations  are  sold  under  this  name,  each  sample  should  be 
tested  for  acidity,  as  som£  consist  of  gelatine  dissolved  in  acetic 
acid,  which  would  soon  cause  fading.  Another  kind  which  the 
author  has  used,  but  cannot  highly  recommend,  is  prepared  by 
dissolving  120  grs.  of  shellac  in  4  drms.  of  methylated  spirit 
by  the  aid  of  heat.  Some  adhesive  mounts  have  been  intro- 
duced into  the  market,  which  are  rather  convenient,  although  the 
author  has  found  them  rather  liable  to  stick  together  at  the  edges; 
but  if  any  amateur  is  desirous  of  making  these,  the  following 
directions  given  by  the  author  in  the  A??iate7tr  Photographer 
will  be  ofjservice  ; — Mix  in  a  small  glass,  mortar,  or  measure,  120 
grs.  of  powder  tragacanth  with  6  drms.  of  rectified  or  methy- 
lated spirit,  and  having  put  9  ozs.  of  water  into  a  pint  bottle — or 
an  old  pyro  bottle  will  do — pour  the  mixed  tragacanth  and  spirit 
quickly  into  the  water  ;  shake  for  a  few  minutes,  and  allow  it  to 
stand  for  twelve  hours,  shaking  it  occasionally,  and  at  the  end  of 
the  time  there  will  be  sufficieat  mucilage  of  tragacanth  to  coat 
100  to  200  mounts.    All  that  is  necessary  to  do  is  to  give  the 

307 


DICTIONARY  OF  PHOTOGRAPHY 


DICTIONARY  OF  PHOTOGRAPHY. 


[Mou 


mounts  a  good  thick  coating  with  a  brush,  allow  it  to  dry,  and 
give  them  a  second  coat.  The  mounts  will  curl  up,  but  they 
can  be  easily  straightened  when  dry. 

Mounting  is  the  operation  of  causing  prints  to  adhere  to 
some  substance,  such  as  card,  cloth,  wood,  or  glass,  either  for 
ornament  or  the  better  protection  of  the  print  itself.  As  the 
mounting  of  a  print  is  in  many  cases  the  making  of  it,  great 
attention  should  be  paid  by  amateurs  to  this  subject.  The 
following  points  should  be  chiefly  regarded  : — The  mount  should 
be  of  a  suitable  colour  and  size,  and  sufficient  margin  should  be 
allowed,  no  excessive  ornamental  lines,  and  the  print  should  be 
accurately  in  the  centre  of  its  mount.  As  the  difficulty  of  placing 
prints  equidistant  from  the  margin  is  one  likely  to  be  met  with 
by  every  amateur,  the  following  hints  may  be  found  useful : — 
After  applying  the  mountant,  lay  the  print  face  downwards  upon 
a  mount  exactly  similar  to  that  upon  which  it  is  desired  to  mount 
the  print,  shift  the  print  about  till  it  is  exactly  in  the  centre  ; 
now  lay  on  top  of  the  print  another  mount  exactly  the  same  size, 
making  the  edges  of  the  two  mounts  coincide:  rub  the  hand 
gently  over  the  top  mount,  when  it  may  be  lifted  up  with  the 
print  in  situ.  Another  ingenious  method,  which  is  recommended 
by  Mr.  T.  C.  Hepworth,  is  as  follows : — Procure  a  piece  of  stout 
carboard — a  mount  will  do — 22  by  15;  draw  diagonals  from 
corner  to  corner,  AC,  bd,  in  sketch,  cutting  each  other  in  centre, 
and  on  these  lines  rectangular  figures  of  the  usual  dimensions  of 
the  trimmed  prints.  For  instance,  the  smallest  may  be  4  by  3 
or  3  by  3,  the  next  4^  by  3^,  5  by  4,  6  by  4,  6  by  5,  7  by  5^,  and 
so  on.  When  it  is  desired  to  mount  a  print,  place  it  face  down- 
wards upon  this  gauge,  when  it  will  be  found  that  it  will  coincide 
with  certain  of  the  lines ;  note  the  number  of  figure,  remove  the 
print,  apply  the  mountant,  and  replace  upon  the  lines  it  covered 
before,  and  place  upon  it  the  mount  which  will  be  found  to 
coincide  with  some  other  set  of  lines  ;  proceed  as  in  the  above 
case,  and  lift  the  mount  and  its  adhering  print ;  use  further 
pressure,  and  roll  or  burnish.  A  very  convenient  little  instrument 
for  those  who  do  not  possess  either  a  burnishing  or  rolling 
machine  is  an  india-rubber  roller  squeegee,  same  as  used  by 
printers,  which  will  cause  absolute  contact  between  the  prints 
and  their  mounts.    For  those  who  possess  a  copying  press, 

309 


Mur] 


DICTIONARY  OF  PHOTOGRAPHY. 


sheets  of  zinc  or  tin  may  be  placed  between  the  mounted  prints, 
and  great  pressure  applied  in  the  ordinary  way ;  whereas  those 
whose  household  appurtenances  include  a  clothes-wringing 
machine  with  india-rubber  rollers,  may,  if  allowed,  use  these  ;  or 
the  bevelled  edge  of  the  cutting  glass  drawn  carefully  over  the  print 
with  some  pressure  will  do  all  that  is  required.  For  mounting 
prints  in  optical  contact  with  glass  the  following  method  answers 
well : — Make  a  solution  of  gelatine  (Nelson's  X  opaque),  20  grs. 
to  every  ounce  of  water,  and  whilst  still  warm  immerse  the  print 
face  downwards  in  it ;  place  the  glass  in  it,  and  after  a  few 
seconds  bring  them  into  intimate  contact,  and  withdraw  from 
solution,  and  squeegee  thoroughly,  and  allow  to  dry.  To  mount 
prints  which  have  an  extremely  glossy  surface,  like  Aristotype, 
etc.,  when  it  is  desired  to  retain  the  high  gloss  which  cannot 
be  done  by  mounting  in  the  usual  way,  squeegee  the  print  on 
to  an  old  negative  glass,  or  cutting  shape,  or  ferrotype  plate,  and 
when  nearly  dry  coat  the  back  with  the  mountant,  and  apply 
to  the  mount ;  use  the  squeegee  vigorously,  and  when  dry  the 
glass  may  be  stripped  off,  leaving  the  print  in  all  its  beauty 
upon  the  mount. 

Muriate  of  Ammonia.   See  Ammonium  Chloride. 

Muriatic  Acid.    See  Hydrochloric  Acid. 

Naturalistic  Photography.  Under  this  title  has  lately 
been  published  one  of  the  most  striking  works  ever  written- 
on  photography,  by  Dr.  P.  H.  Emerson.  Naturalistic  Photo- 
graphy is  an  attempt  to  render  by  means  of  the  usual  tools 
and  operations  of  photography  the  same  as  given  by  the  so- 
called  "  Impressionist"  school  of  painting,  of  which  Whistler  is 
the  leader.  As  perhaps  the  clearest  exposition  of  the  teaching 
and  aim  of  this  school,  we  cannot  do  better  than  refer  to  Dr. 
Emerson  himself,  who  says  that  a  picture  "should  be  made 
just  as  sharp  as  the  eye  sees  it,  and  no  sharper ;  for  it  must  be 
remembered  the  eye  does  not  see  things  as  sharply  as  the 
photographic  lens,  for  the  eye  has  the  faults  due  to  dispersion, 
spherical  aberration,  astigmatism,  aerial  turbidity,  blind  spot, 
and  beyond  twenty  feet  it  does  not  adjust  perfectly  for  the 
different  planes.  All  these  slight  imperfections  make  the  eye's 
vision  more  imperfect  than  that  of  the  optician's  lens,  even  when 
objects  in  one  plane  only  are  sharply  focussed ;  therefore,  except 

310 


DICTIONARY  OF  PHOTOGRAPHY 


[Nit 


in  very  rare  cases,  which  will  be  touched  upon  elsewhere,  the 
chief  point  of  interest  should  be  slightly — very  slightly — out  of 
focus,  while  all  things,  out  of  the  plane  of  the  principal  object,  it 
is  perfectly  obvious  from  what  has  been  said,  should  also  be 
slightly  out  of  focus,  not  to  the  extent  of  producing  destruction 
of  structure  or  fuzziness,  but  sufficiently  to  keep  them  back  and 
in  place.  .  .  .  The  rule  in  focussing,  therefore,  should  be,  focus 
for  the  principal  object  of  the  picture,  but  all  else  must  not  be 
sharp ;  and  even  that  principal  object  must  not  be  as  perfectly 
sharp  as  the  optical  lens  will  make  it.  It  will  be  said,  But  in 
Nature  the  eye  wanders  up  and  down  the  landscape,  and  so 
gathers  up  the  impressions,  and  all  the  landscape  in  turn  appears 
sharp.  But  a  picture  is  not  1  all  the  landscape  ' ;  it  should  be 
seen  at  a  certain  distance — the  focal  length  of  the  lens  used,  as 
a  rule  ;  and  the  observer,  to  look  at  it  thoughtfully,  if  it  be  a 
picture,  will  settle  on  a  principal  object,  and  dwell  upon  it,  and 
when  he  tires  of  this  he  will  want  to  gather  up  suggestions  of 
the  rest  of  the  picture."  Whilst  not  agreeing  with  Dr.  Emerson 
in  toto,  the  author  refrains  from  any  criticism  of  a  work  of  which 
the  writer  says,  "It  is  always  fairer  to  read  an  author's  writings 
than  to  read  the  stupid  constructions  put  upon  them  by  untrained 
persons." 

Negative  is  the  term  applied  to  the  image  in  which  the  lights 
and  shades  are  reversed.  These  can  be  made  by  direct  action 
of  light  in  the  camera,  or  by  printing  in  a  frame  from  a  positive 

Negative  Storing.  To  the  amateur  whose  work  is  frequent 
and  successful  the  stock  of  negatives  soon  becomes  considerable, 
and  the  question  of  storage  a  bugbear.  Many  use  the  grooved 
negative  boxes,  but  while  these  are  convenient  their  bulk  is  a 
great  objection.  The  best  plan  is  to  use  paper  negative  bags, 
on  which  can  be  written  the  subject,  date,  and  duration  of 
exposure,  aperture  of  diaphragm,  mode  of  development,  and 
any  other  remarks  which  may  be  considered  necessary.  The 
negatives  in  the  bags  can  then  be  packed  close  together  in  boxes 
not  grooved,  and  they  will  take  up  about  one-fourth  of  the 
room  of  grooved  boxes.  An  index  can  be  kept  of  them,  and  a  list 
can  be  pasted  inside  the  lid  of  each  box  for  further  reference. 

Nitric  Acid  (Ger.,  Salpetersiiure ;  Fr.,  Acidc  Nitriquc). 
HN03  =  63.    Synonym:  Aquafortis.     Prepared  by  distillation 

3ii 


Nit] 


DICTIONARY  OF  PHOTOGRAPHY. 


from  Chili  saltpetre  (nitrate  of  soda)  and  sulphuric  acid.  Specific 
gravity,  1*45.  A  heavy  colourless  liquid  fuming  in  the  air.  It  is 
extremely  poisonous,  having  a  most  powerful  corrosive  action  ; 
2  drms.  is  the  smallest  fatal  dose  known — the  antidote,  any 
alkaline  earthy  carbonate,  as  chalk,  lime,  magnesia. 

Nitro-Hydrochloric  Acid  (Ger.,  Konigswasser ;  Fr.,  Eau 
regale).  Synonym :  Aqua  regia.  A  mechanical  mixture  of  3 
parts  of  hydrochloric  acid  with  1  part  of  nitric  acid  ;  the  oxygen 
of  the  latter  combines  with  the  hydrogen  of  the  former,  setting 
free  chlorine,  and  forming  water  2HCI  +  HN03=H20  +  Cl2  +  N02 
It  is  used  to  dissolve  gold  for  the  preparation  of  gold  perchloride, 
the  principal  agent  for  which  purpose  being  the  free  chlorine. 

Non-Actinic  Rays.   See  Spectrum. 

Obernetter's  Process,  or  Lichtkupferdruck.  A  mechanical 
printing  process  of  very  ingenious  idea  and  of  extremely  pleasing 
and  artistic  results.  The  metallic  image  of  silver  of  a  gelatine 
positive  is  converted  into  chloride  of  silver,  and  the  film  is  then 
stripped  and  applied  to  the  surface  of  a  copper  plate,  and,  under 
the  influence  of  a  voltaic  current,  the  silver  chloride  is  decom- 
posed, and  the  chlorine  unites  with  the  copper  and  etches  it  to 
a  greater  or  less  degree,  according  to  the  depth  of  deposit  of 
silver  chloride.  The  result  is  a  grained  intaglio  plate  of  extreme 
delicacy  and  beauty,  which  is  inked  and  printed  from  the  same 
as  any  ordinary  etching. 

Objective.    A  term  sometimes  applied  to  the  lens. 
Oil  of  Lavender.   See  Lavender,  Oil  of. 
Oil  of  Spike.   See  Spike,  Oil  of. 
Oil  Paintings,  to  Copy.   See  Copying. 
Opacity.    See  Density. 

Opalotype.  A  term  applied  to  pictures  on  opal  glass.  They 
can  be  made  by  coating  opal  glass  with  a  plain  gelatino-bromide 
emulsion,  or  by  using  a  printing-out  emulsion.  The  exposure 
and  development  are  the  same  as  for  bromide  paper.  Either 
polished  or  ground  opal  glass  may  be  used,  the  latter  giving 
very  pleasing  pictures  of  a  matt  surface.    Another  method  of 

312 


DICTIONARY  OF  PHOTOGRAPHY. 


[Opa 


obtaining  pictures  by  the  printing-out  process  is  by  the  use  of 
a  collodio-chloride  emulsion,  which  may  be  made  as  follows : — 

No.  i. 

Silver  nitrate    31  grs.    or     2  grms. 

Methylated  ahohol   28  drms.     100  c.cm. 

Dissolve  by  the  aid  of  heat  immediately  before  using. 

No.  2. 

Strontium  chloride   31  grs.    or     2  grms. 

Methylated  alcohol   28  drms.  ,,  100  c.cm. 

No.  3. 

Citric  acid    31  grs.    or     2  grms. 

Methylated  alcohol   28  drms.     100  c.cm. 

No.  4. 

Pyroxyline  or  celloidin      ...  62  grs.    or     4  grms. 

Methylated  alcohol   28  drms.  ,,  100  c.cm. 

„        ether    28     „     ,,  100 

To  make  the  emulsion 

Take  of  No.  2    150  mins.  or     9  c.cm. 

No.  3    150    „     „     9  „ 

„      No.  4    28  drms.      100  ,, 

Mix,  and  add  gradually,  with  constant  agitation, 

No.  1   ...       ...     75  mins.  or  4*5  c.cm. 

Give  the  plates  an  edging  of  albumen  or  india-rubber  solution 
a  quarter  of  an  inch  broad,  and,  after  coating,  allow  them  to  dry 
thoroughly.  The  prints  should  be  washed,  toned,  and  fixed  in 
the  same  way  as  ordinary  silver*  prints  or  the  sulpho-cyanide 
toning  bath  may  be  used  with  better  effect.  (See  Toning.)  As 
it  is  necessary  to  examine  the  opal  during  the  operation  of 
printing,  it  is  obvious  that  some  arrangement  must  be  made  for 
replacing  it  in  exactly  the  same  position.  Printing  frames  may 
be  obtained  commercially  specially  adapted  for  this  work,  but 
an  ordinary  printing  frame  may  be  utilised  in  the  following 
manner :  —Replace  the  hinged  back  by  a  solid  piece  ol  wood  fa 

3X3 


Opt] 


DICTIONARY  OF  PHOTOGRAPHY. 


of  an  inch  less  in  thickness ;  coat  the  inside  of  this  back  with  a 
composition  of  gelatine  made  as  follows  : — 

Gelatine  (Nelson's  X  opaque)       I  oz.   or     2  grms.  . 

Water    4  ozs.  „  132  c.cm. 

Glycerine     ...       ...       ...       2  „  56 

Soak  the  gelatine  in  water,  and  dissolve  by  the  aid  of  heat ; 
add  the  glycerine  last.  The  opals  will  adhere  to  this  on  being 
damped,  or  a  thick  india-rubber  solution,  with  a  little  castor  oil 
added,  may  be  used  : — 

Pure  masticated  rubber     ...     40  grs.    or    2  grms. 
Castor  oil     ...       ...       ...      10  drops  ,,  0*6  c.cm. 

Benzole    ...       1  oz.     „  25  „ 

A  small  spot  of  this  at  each  corner  will  cause  the  opal  to  adhere 
firmly  to  the  wood.  To  keep  the  negative  in  position,  a  screw 
may  be  driven  through  one  end  of  the  printing  frame,  and  the 
point  of  the  screw  cut  off ;  a  groove  cut  in  it  in  which  to  fit  the 
negative.  To  the  back  affix  three  or  four  small  tongues  of  metal 
pierced  with  holes,  which  holes  may  drop  over  pins  driven  into 
the  sides  of  frame,  or  the  back  may  be  permanently  fixed  by  a 
hinge  to  one  end  of  the  frame. 

Optical  Centre.  In  every  lens  exists  a  point  situated  in  its 
principal  axis,  any  incident  ray  passing  through  which  point 


Fig.  76. 


does  not  suffer  deviation ;  this  is  termed  the  optical  centre. 
None  but  single  lenses  have  true  optical  centres,  but  the  optical 
centre  may  be  approximately  found  in  an  achromatic  combina- 

3H 


DICTIONARY  OF  PHOTOGRAPHY.  [Oxa 

tion  by  considering  it  as  a  single  lens.  To  find  the  optical  centre 
of  a  lens  draw  a  line  to  represent  the  principal  axis,  a  c  a'  ;  then 
from  the  centres  of  curvature  draw  two  radii,  ab  and  a'b', 
parallel  to  one  another,  but  oblique  to  the  central  axis  ;  then  join 
their  extremities,  b,  b',  and  the  point  c  at  which  the  principal 
axis  is  cut  by  this  line  is  the  optical  centre.  To  find  the  optical 
centre  of  a  meniscus  lens  prolong  b  b'  till  it  meets  the  principal 
axis ;  the  optical  centre  of  plano-concave  and  plano-convex 
lenses  is  found  by  the  intersection  of  the  spherical  surfaces  by 
the  principal  axis. 

Optical  Lantern.    See  Magic  Lantern. 

Optics.  That  branch  of  science  relating  to  the  nature  and 
laws  of  vision.  The  subject  is  too  comprehensive  to  treat  here. 
For  further  study  the  amateur  is  referred  to  Glazebrook's 
"  Physical  Optics." 

Orange  Light.  Actinic  light  filtered  through  any  medium 
which  absorbs  all  but  the  orange  rays.  It  is  frequently  used  for 
the  illumination  of  the  dark-room,  and  is  perfectly  safe  if  not  too 
brilliant. 

Orthographic  and  Orthoscopic.  Two  fanciful  titles  given 
to  certain  classes  of  lenses. 

Osmose.  The  action  that  takes  place  when  two  liquids  of 
differing  densities  are  separated  by  a  permeable  medium.  (See 
Dialyser.) 

Over-Exposure  is  the  undue  prolongation  of  the  exposure  of 
the  sensitive  surface,  and,  as  the  author  has  endeavoured  to 
show,  the  ill  effects  can  be  corrected  by  careful  development. 
The  effect  of  over-exposure  on  the  sensitive  surface  is  that  the 
image  starts  up  quickly,  and  the  plate  shows  signs  of  Fogging 
(q.v.)  before  proper  density  is  obtained,  the  resulting  negative 
being  thin,  but  full  of  detail. 

Oxalate  Developer.   See  Developer. 

Oxalic  Acid  (Ger.,  Oxalsdurc ;  Fr.,  Acide  Oxalique).  H2C>04, 
2H20=i26.  Prepared  by  oxidation  of  sugar  or  sawdust  by 
nitric  acid.  It  is  recommended  for  acidifying  the  oxalate  of 
potash  solution  for  ferrous  oxalate  developer,  but  its  chief  use  is 
in  the  preparation  of  oxalate  of  potash,  ferric  oxalate,  and  other 

315 


Oxg] 


DICTIONARY  OF  PHOTOGRAPHY. 


stable  salts.  It  is  extremely  poisonous  (60  grs.  being  sufficient 
to  cause  death) ;  its  antidote,  magnesia,  chalk,  or  lime  in  any 
form,  with  which  it  forms  insoluble  oxalate  of  lime.  Solubility : 
1  in  15-5  of  cold  water,  1  in  1  of  boiling;  sparingly  soluble  in 
alcohol. 

Ox-Gall.  The  fresh  gall  of  the  ox  purified,  and  evaporated 
to  a  suitable  consistency.  It  is  used  photographically  to  make 
water-colours  take  to  the  surface  of  albumenised  prints.  It 
should  be  obtained  from  a  chemist's,  and  in  this  state  is  a  sticky, 
rather  offensive-smelling  mass.  It  is  soluble  in  water  and  spirit, 
and  can  be  dissolved  in  either,  or,  preferably,  a  mixture  of  both, 
and  applied  to  surface  of  print  with  camel's-hair  pencil. 

Oxygen.  O  =  16.  A  gaseous  element  of  ordinary  tempera- 
tures, forming  |  by  weight  of  water,  and  \\  of  the  air  ;  it  is  about 
the  most  abundant  element  known,  entering  into  the  composition 
of  all  animal  and  vegetable  tissues,  and  about  half  the  weight  of 
the  solid  earth.  It  is  used  in  the  oxy-hydrogen  light,  and  is 
usually  prepared  by  heating  a  mixture  of  chlorate  of  potash  and 
black  oxide  of  manganese. 

Oxy-Hydrogen,  and  Oxy-Calcium  or  Drummond's  Light. 

Both  are  so  much  alike  that  but  one  description  is  required.  A 
cylinder  or  ball  of  lime  is  placed  in  the  focus  of  a  parabolic 
mirror,  and  a  lighted  jet  of  oxygen  and  hydrogen  or  coal  gas  is 
directed  upon  it.  The  lime  burns  with  an  exceedingly  intense 
flame,  which  can  be  seen  at  night  in  hazy  weather  a  distance  of 
sixty  miles,  and  in  clear  weather  over  a  hundred  miles.  The 
oxy-calcium  light  differs  but  slightly,  the  flame  of  a  spirit-lamp 
being  used  instead  of  hydrogen. 

Packing  Plates.  Several  methods  are  employed  by  commer- 
cial firms  to  preserve  dry  plates  from  accidental  injury  and 
fracture  whilst  travelling,  but  the  best  method  is  that  practised 
by  a  well-known  London  firm,  whose  method  is  as  follows  : — 
Absolutely  pure  tissue  paper  is  cut  the  exact  width  of  the  plates, 
but  sufficiently  long  to  enclose  five  or  six  plates  ;  stout  card  cases, 
just  a  shade  larger  than  the  plate,  and  a  strip  of  non-actinic 
paper,  are  placed  lengthwise  in  the  box,  with  free  ends  projecting  ; 
then  a  sheet,  or  the  commencement  of  a  sheet,  of  tissue  paper ; 
a  plate  is  laid  face  downwards,  and  the  tissue  paper  folded  over 

316 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pan 


the  back  of  it ;  then  another  plate  is  laid  face  downwards  on  the 
tissue  paper,  and  this  is  continued  till  the  case  is  full,  when  the 
free  ends  of  the  non -actinic  paper  are  folded  over;  the  whole  is 
then  wrapped  in  black  paper,  slipped  into  another  case,  and  that 
into  the  outer  box.  By  alternating  the  plates  and  paper  in  this 
manner,  any  number  of  plates  may  be  safely  carried  by  road  or 
rail  without  any  fear  of  fracture.  As  some  amateurs  may  desire 
to  travel  abroad — and  the  Custom-house  officer  is  their  bugbear 
— the  following  labels  may  be  useful : — 

English. — Photographic  dry  plates.  To  be  opened  only  in 
ruby  light. 

Fre?ich. — Plaques  seches  photographiques.  A  ouvrir  seule- 
ment  avec  eclairage  couleur  rubis. 

Italian. — Lustra  da  seccare  fotografiche.  Da  aprire  solamente 
con  illuminazione  colore  di  rubino. 

Getman. — Photographische  Trocken  Platten.  Nur  bei  dunkel- 
rother  Beleuchtung  zu  offnen. 

Spanish. — Planchas  secas  para  fotografia.  Abrase  el  paquete  en 
un  cuarto  oscuro  y  a  la  luz  rubi. 

Dutch. — Photographiche  drooze  platen.  On  open  gemaakt 
te  worden  alleen  im  roode  licht. 

Swedish. — Ljuskaushga  fotografiska  platar,  blivfa  forstorda  om 
de  uttsattas  forljus.  Fas  derfore  ej  oppuas  utom  i  ett  absolut 
morkt  rum. 

Or  the  two  following,  in  French  and  German,  are  a  little  more 
explicit : — 

French.— Plaques  photographiques  sensibles.  Abimees  par 
exposition  a  la  lumiere.  Prendre  garde  de  n'ouvrir  la  boite  que 
dans  une  chambre  parfaitement  obscure. 

Germa?i. — Photographische  Trocken  Platten,  werden  verdor- 
ben  in  dem  Lichte  ausgesetzt.  Mussen  also  nur  in  einem 
absolut  dunkeln  Zimmer  geoffnet  werden. 

Palladium.  Pd=  106.  A  metallic  element  sometimes  found 
native  in  the  pure  state,  and  frequently  mixed  with  platinum, 
which  it  much  resembles.  It  has  been  recommended  for  toning 
transparencies  and  enamels  in  the  form  of  chloride,  but  its  use 
is  limited. 

'  Panel.  The  style  of  a  commercial  photograph,  size  about 
4  by  8^  ins. 

317 


Pap] 


DICTIONARY  OF  PHOTOGRAPHY. 


Paper,  Albumenised.   See  Albumenised  Paper. 

Paper,  Plain  or  Matt-surfaced.   See  Sensitised  Paper. 

Paper,  Sensitised.   See  Sensitised  Paper. 

Papyrotype,  or  Papyrography.  A  modification  of  photo- 
lithography, in  which  paper  is  used  as  the  support,  instead  of  a 
stone  or  metal  plate. 

Parabola  is  the  curve  described  by  a  moving  point,  which  is 
always  at  the  same  distance  from  a  fixed  line,  its  directrix,  that  it 
is  from  a  fixed  point,  its  focus.  The  chief  use  in  photography  .of 
the  parabola  is  in  the  construction  of  mirrors  or  reflectors  for 
artificial  light  from  the  fact  that  the  rays  of  a  light  placed 
in  the  focus  of  a  parabolic  mirror  will  be  reflected  in  parallel 
rays. 

Paste.    See  Mountant. 

Paste,  Encaustic.   See  Encaustic  Paste. 

Pearlash.   A  synonym  for  impure  Potassium  Carbonate  (g.v.). 

Pellet's  Process.   See  Cyanotype. 

Pellicle.  Literally  a  thin  skin  or  film,  and  in  this  sense 
applied  to  the  emulsion  when  the  solvents  are  evaporated. 
Pellicular  films  were  introduced  many  years  back,  and  were  one 
of  the  first  adaptations  of  gelatine  to  photography. 

Pencil  of  Light.  A  term  applied  to  the  rays  of  light  pro- 
ceeding from  any  luminous  body.  When  the  object  is  near,  the 
pencil  or  rays  of  light  are  divergent  rays  ;  when  the  object  is 
very  distant,  the  pencils  may  be  considered  parallel.  A  pencil, 
the  rays  of  which  lessen  as  it  proceeds,  is  said  to  be  convergent. 

Perspective  is  the  art  of  representing  solid  bodies  on  a  plane 
surface.  It  is  divided  into  two  branches — linear  perspective, 
which  shows  the  apparent  forms  of  objects  on  the  prospective 
outlines  ;  and  aerial  perspective,  which  distinguishes  the  distance 
of  objects  by  the  relative  brilliancy  of  their  colour.  The  subject 
is  much  too  comprehensive  to  treat  here.  The  amateur  who 
desires  to  learn  the  rules  of  perspective  must  refer  to  some  of 
the  manuals  on  this  subject. 

'  Phosphorus.  P  =  31.  A  non-metallic  element  widely  dis- 
tributed throughout  the  animal  and  vegetable  kingdom,  but 

318 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pho 


never  occurring  in  the  free  state.  It  is  insoluble  in  water, 
soluble  in  ether,  chloroform,  benzine,  turpentine,  and  other  oils, 
and  bisulphide  of  carbon.  It  is  prepared  from  bone-ash  and 
other  phosphates  by  treatment  with  sulphuric  acid  and  sublima- 
tion with  charcoal  and  sand.  It  has  but  little  interest  photo- 
graphically, phosphoric  acid,  a  compound,  being  but  rarely  used. 

Photo-Engraving.  Numerous  processes  are  in  every-day 
use,  in  the  best  of  which  the  action  of  light  upon  a  bituminous 
film  is  taken  advantage  of.  As  these  processes  are  hardly  within 
the  scope  of  the  general  run  of  amateurs,  no  further  mention  will 
be  made.  The  best  handbook  on  the  aubject  is  W.  T.  Wilkinson's 
"  Photo-Mechanical  Processes." 

Photography  is  the  art  of  obtaining  the  representation  of 
objects  by  the  agency  of  light  upon  sensitive  substances.  The 
following  is  a  short  history  of  the  rise  and  progress  of  the  art : — 
In  the  sixteenth  century  Baptista  Porta,  a  Neapolitan,  invented 
the  Camera  Obscura  (q.v.),  and  this  was  used  to  obtain  sketches 
by  hand  of  the  objects  projected  by  the  lens.  In  1777  Scheele, 
the  great  chemist,  discovered  the  important  fact  that  chloride  of 
silver  blackened  in  sunlight,  the  chief  action  lying  in  the  violet 
end  of  the  spectrum.  In  1802,  Thomas  Wedge  wood,  son  of  the 
famous  potter,  published  in  the  "Journal  of  the  Royal  Institu- 
tion "  an  account  of  a  method  of  copying  paintings  on  glass,  and 
of  making  profiles  by  the  agency  of  light  upon  nitrate  of  silver. 
In  the  experiments  which  are  thus  described  he  was  assisted  by 
Sir  Humphrey  Davy.  They  managed  to  obtain  images  upon 
paper  and  white  leather  by  means  of  the  solar  microscope,  but 
were  unable  to  fix  them;  therefore  the  image  was  soon  obliterated 
by  the  darkening  of  the  whole  surface.  In  1814  Nicephore  de 
Niepce  commenced  a  series  of  experiments,  but  although  he 
managed  to  obtain  images  upon  a  bituminous  film,  the  process 
was  impracticable  for  ordinary  purposes,  from  the  inordinate 
exposure  (several  hours)  which  was  required.  He  then,  in 
partnership  with  Daguerre,  carried  on  his  experiments  ;  but  it  was 
not  until  1839,  s™  years  after  Niepce's  death,  that  Daguerre 
communicated  to  the  Acad6mie  des  Sciences  at  Paris  the  process 
so  well  known  as  Daguerreotype.  Early  in  1839  Fox  Talbot, 
previous  to  Daguerre's  communications,  announced  to  the  Royal 
Society  a  method  of  "  photogenic  drawing,"  in  which  pictures 

3*9 


Pho] 


DICTIONARY  OF  PHOTOGRAPHY. 


were  produced  upon  paper  prepared  with  chloride  of  silver.  Fox 
Talbot  effected  the  fixation  of  these  pictures  by  saturated 
solutions  of  chloride  of  sodium  and  bromide  of  potassium.  The 
use  of  hyposulphite  of  soda,  however,  soon  became  general,  Sir 
Humphrey  Davy  having,  in  1821,  published  the  action  of  this  salt 
upon  the  salts  of  silver.  In  1841  Fox  Talbot  patented  his 
process  called  Talbotype  or  Calotype  (q.v.).  To  the  Rev.  J.  B. 
Reade  is  due  the  credit  of  first  recommending  a  developer, 
although  Fox  Talbot  was  the  first  to  use  a  restrainer.  Up  to 
this  point  paper  negatives  alone  were  in  use;  but  in  1848  a 
cousin  of  the  original  Niepce,  M.  Niepce  de  St.  Victor,  proposed 
the  use  of  albumen  on  glass  as  a  vehicle  for  the  sensitive  salts 
of  silver.  These  plates,  however,  were  very  insensitive,  and 
numerous  substances,  such  as  starch,  gelatine,  gum,  etc.,  were 
proposed;  none,  however,  were  successful.  In  185 1  Le  Gray, 
of  Paris,  and  Scott  Archer,  of  London,  proposed  the  use  of 
collodion,  the  latter  publishing  such  a  complete  description  of 
the  wet  collodion  process  that  but  little  improvement  has  ever 
been  effected.  A  great  disadvantage,  however,  of  this  process 
was  the  necessity  of  exposing  the  film  whilst  wet,  necessitating 
the  use  of  bulky  and  heavy  impedimenta  for  the  landscape 
photographer,  in  the  shape  of  dark  tent,  etc.  It  was  then  dis- 
covered that  the  application  of  certain  organic  substances  to  the 
washed  film  would  allow  of  the  plates  being  used  in  the  dry 
state.  In  1862  Major  Russell  discovered  the  use  of  alkaline 
pyrogallol  as  a  developer,  and  his  accidental  discovery  of  the 
restraining  power  of  the  soluble  bromides  gave  the  first  impetus 
to  the  manufacture  of  bromide  of  silver  films,  which  could  be 
exposed  dry.  In  1864  Messrs.  Sayce  and  Bolton  described  the 
process  of  collodion  emulsion  making,  which  was  poured  upon 
glass  plates,  and  then  washed  to  free  from  inert  salts.  In  1874 
it  was  discovered  that  the  emulsion  might  be  washed  previous 
to  use,  and  in  1871  Dr.  R.  L.  Maddox  published  the  first  notice 
of  a  gelatine  emulsion,  and  from  that,  in  1878,  Mr.  Charles 
Bennet  discovered  the  capabilities  of  the  process  and  power  of 
increasing  the  sensitiveness  by  digestion  at  high  temperatures. 
Since  then  the  process  has  been  most  rapid,  the  ammonia  pro- 
cess becoming  known,  and  rapid  films  and  plates  being  of  every- 
day occurrence.  During  the  last  few  years  film  photography  has 
become  quite  a  standard  process,  and  increased  active  inventive- 

320 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pho 


ness  upon  the  part  of  commercial  firms  has  improved  these  till 
but  little  ;  improvement  seems  necessary.  Of  the  application  of 
photography  in  every-day  life  it  would  be  almost  impossible  to 
treat ;  the  various  mechanical  printing  methods,  the  use  of 
photography  for  supplying  pictures  for  illustrated  papers,  cata- 
logues, price  lists,  etc.,  are  too  well  known  to  need  any  descrip- 
tion. Its  use  in  astronomy  for  making  charts  of  the  celestial 
bodies,  in  the  interests  of  justice  for  the  detection  of  criminals, 
for  the  purposes  of  experimental  warfare  and  as  an  assistant  in 
scientific  research,  for  sounding  the  depths  of  the  sea  and  for 
pathological  study  in  medicine,  seems  almost  unlimited. 

Photography  in  Natural  Colours.  The  methods  of  repro- 
ducing objects  in  the  colours  of  nature  may  practically  be  divided 
into  three  heads:  (i)  by  the  use  of  subchloride  of  silver;  (2) 
by  Lippmann's  process,  or  the  production  of  interference  waves  ; 
and  (3)  by  the  heliochromic  or  three-colour  sensation  process. 
The  first  process  is  that  which  was  experimentally  examined  by 
Seebeck,  Becquerel,  Niepce  de  St.  Victor,  Poitevin,  Kopp,  etc., 
and  practically  consists  of  exposing  subchloride  of  silver  to 
the  coloured  rays,  either  of  the  spectrum  or  beneath  a  coloured 
glass  positive,  etc.  The  disadvantage  of  this  process  is  that  there 
is  no  means  of  fixing  the  colours  which  are  thus  obtained,  and 
consequently  the  results  will  not  bear  a  prolonged  exposure  to 
light.  Some  of  the  most  successful  results  can  be  obtained  by 
using  commercial  gelatino-  or  collodio-chloride  paper,  and  treat- 
ing it  as  suggested  by  Kopp.  The  paper  should  be  exposed  to 
diffused  light  whilst  immersed  in  the  following  solution  till  it 
turns  blue-green  : — 

Chloride  of  zinc      ...    ...       015  grms. 

Sulphuric  acid        ...       ...    2  drops 

Water    ...    150  c.cm. 

The  paper  can  then  be  well  washed  and  dried  between  blotting 
paper  and  kept  in  the  dark.  It  will  keep  in  this  state  for  some 
time.    The  following  solution  should  be  prepared  : — 

Potassium  bichromate  (pure)    15  grms. 

Cupric  sulphate  (pure)    ...      15  „ 

Water    ...       ...    100  c.cm. 


If  necessary  the  ingredients  should  be  dissolved  with  heat. 

321  Y 


Pho] 


DICTIONARY  01  PHOTOGRAPHY. 


Mercurous  nitrate,  15  grs.,  should  also  be  dissolved  in  as  small  a 
quantity  of  water,  acidulated  with  nitric  acid,  as  possible  ;  the 
two  solutions  mixed,  both  being  at  21 2°  F. ;  the  mixture  fil- 
tered, and  the  total  bulk  of  the  solution  brought  up  to  100  c.cm. 
The  blue-green  paper  is  bathed  in  this  for  a  minute,  well  drained, 
and  then  immersed  in  a  3  per  cent,  solution  of  zinc  chloride  or 
nitrite  of  soda  till  it  turns  blue  again,  then  blotted  off  between 
blotting  paper,  and  exposed  whilst  damp  under  the  coloured 


Fig.  77. 

object.  After  exposure  it  will  be  seen  that  the  green  and  yellow 
will  be  visible,  but  the  other  colours  require  developing,  and  for 
this  the  green  and  yellow  must  be  covered  with  a  varnish,  and 
then  the  paper  immersed  in  a  dilute  2  per  cent,  solution  of  sul- 
phuric acid.  In  order  to  fix  the  print  to  some  extent,  it  should  be 
immersed  in  the  mercury  bath,  then  into  the  chloride  of  zinc  ; 
wash  and  dry  between  blotting  paper,  and  then  coat  with  a 
solution  of  gum  arabic  with  5  per  cent,  of  sulphuric  acid  added. 


Fig.  78. 


The  explanation  of  the  theory  of  the  formation  of  these  colours 
is,  according  to  Zenker,  precisely  the  same  as  that  involved  in 
the  following  process  : — 2.  The  interference  method  of  Lippmann 
was  announced  by  him  in  February  1891.  This  is  founded  on 
the  theory  of  stationary  waves,  propounded  by  Zenker  and 
Wiener.  Let  us  assume  abed,  fig.  78,  to  be  a  ray  of  light 
proceeding  in  the  direction  of  a  d,  and  the  small  dots  to  be  the 
particles  of  ether  vibrating  or  in  rapid  motion,  and  on  its  reaching 
d  it  meets  with  some  reflecting  surface  which  sends  the  ray  back. 
We  shall  have  the  second  ray  proceeding  along  the  same  line  but 

322 


DICTIONARY  OF  PHOTOGRAPHY.  [PllO 

in  the  opposite  phase,  and  at  b  and  c  the  pull  or  vibratory 
motion  of  the  ether  particle  will  be  equal  in  both  directions,  as 
shown  by  the  small  arrows  ;  so  that  at  these  points  there  will  be 
no  light,  whilst  in  the  loops  in  between  there  will  be  increased 
light.     Now  in  fig.  77  we  see  a  ray  of  light  proceeding  in 
the   direction  A  B ;  and   the  arrows  represent  the  vibratory 
motion  of  the  particles  of  ether,    a  d  or  c  b  is  a  complete  wave 
length.    Now  by  referring  to  fig.  78  it  is  obvious  that  the  point  b 
is  exactly  half  a  wave-length  from  a  and  c,  and  c  exactly  half  a 
wave-length  from  b  and  d\  so  that  we  get  no  light  at  points 
which  are  exactly  half  a  wave-length  apart.    If  a  ray  of  light  thus 
treated  passed  through  a  film  of  sensitive  material,  it  is  obvious 
that  where  we  get  no  light  we  shall  have  no  chemical  action, 
and  consequently  no  deposit  of  silver  ;  whilst  in  between  these 
places  we  shall  get  a  deposit ;  and  a  film  of  this  character,  after 
development,  will  only  reflect  that  light  which  has  a  wave-length 
just  double  the  distance  between  the  reflecting  particles  of  silver  ; 
consequently  we  get  a  reproduction  of  the  colour  which  caused 
this  deposit.    Lippmann  used  first  of  all  Taupenot's  albumen 
process,  which  consists  practically  of  using  iodide  of  silver  sus- 
pended in  albumen  ;  later  he  used  bromide  of  silver  suspended 
in  albumen  ;  but  he  met  with  one  great  difficulty,  and  one  which 
every  practical  photographer  meets  with  in  ordinary  practice,  and 
that  is  that  the  silver  salts  are  more  sensitive  to  the  blue  and 
violet  than  to  any  other  colour,  or,  to  put  it  more  popularly,  the 
photographic  plate  sees  the  blue  and  violet  as  the  brightest  part 
of  the  spectrum  ;  therefore  he  exposed  his  spectrum  in  sections, 
using  a  deep  orange-red  screen  and  giving  one  hour's  exposure 
to  get  the  red,  and  then  five  to  ten  minutes  for  green  with  a 
yellow  screen,  and  a  very  pale  yellow  screen  and  twenty  to  thirty 
seconds'  exposure  for  the  blue.     After  exposure  the  plates  were 
developed  with  pyrogallol,  and  fixed,  washed  and  dried.  Natu- 
rally, when  the  accounts  of  Lippmann's  experiments  were  pub- 
lished, and  the  results  confirmed,  many  had  a  good  try  to  do  the 
same  thing.    Kron6  of  Dresden  was  one  of  the  first,  and  he  used 
albumen  plates,  but  instead  of  mercury  he  used  black  velvet. 
Chas.  R.  Thwing,  in  1892,  used  collodio-bromide  plates,  and  re- 
duced the  exposure  to  twenty  minutes  in  the  sun.    M.  de  St. 
Florent,  in  1892,  exposed  an  ordinary  gelatino-bromide  plate 
with  an  orange  screen  under  a  coloured  transparency,  and  then, 

323 


Pho] 


DICTIONARY  OF  PHOTOGRAPHY. 


without  developing,  fixed  and  washed  it ;  and  it  was  said  this 
plate  whilst  damp  reproduced  the  colours.  In  1892  MM.  Auguste 
and  Louis  Lumiere  showed  at  a  meeting  of  the  Societe  des 
Sciences  Industrielles  of  Lyons  some  spectra  produced  by 
Lippmann's  method  which  were  superior  in  brilliancy.  These 
were  made  on  gelatino-bromide  plates.  In  1892  Valenta  pub- 
lished some  experiments  on  the  preparation  of  such  an  emulsion, 
and  a  year  later  Lumiere  published  their  formula.  Valenta's 
process  is  as  follows  : — 

A.  B. 

Gelatine    10  g.  Gelatine   1  1    20  g. 

Water    300  c.cm.  Water    300  c.cm. 

Silver  nitrate    ...  6  g.  Potassium  bromide    5  g. 

The  solutions  should  be  cooled  to  30°-35°  C,  and  then  solution  A  . 
gradually  added  to  solution  B,  with  constant  stirring,  and  a  faint 
opalescent  or  almost  transparent  liquid  is  obtained,  which  is 
immediately  poured  into  about  1  litre  of  90  per  cent,  alcohol,  and 
well  stirred  till  the  gelatine  emulsion  clings  to  the  glass  rod.  It 
is  then  cut  up  into  small  pieces,  washed  in  running  water  for  a 
short  time,  and  made  up  to  the  original  bulk  (600  c.cm.)  with 
water,  melted  and  filtered,  for  which  purpose  Valenta  strongly 
recommends  fine  Italian  hemp,  well  washed  with  caustic  potash 
and  water  or  glass  wool.  After  filtration  the  emulsion  is  colour- 
sensitised  with  some  dye  and  coated.  Valenta  states  that,  after 
the  emulsion  has  set,  the  plates  should  be  soaked  in  dilute 
alcohol,  and  rocked  till  the  small  air  bubbles,  which  adhere  very 
firmly  to  the  film,  are  no  longer  visible.  They  should  then 
be  washed  under  a  tap,  and  dried.  To  render  these  plates 
colour-sensitive  alcoholic  solution  of  cyanine  1  :  500  is  used,  and 
either  1-2  c.cm.  of  this  is  added  to  every  100  c.cm.  of  emulsion 
before  coating,  or  the  plates  can  be  bathed  after  coating  in  a  bath 
of  1-5  c.cm.  of  above  solution  in  100  c.cm.  of  water.  Better 
results  are  obtained  by  mixing  cyanine  and  erythrosin  as  follows  : 
Cyanine  solution  (1  :  500)  4  c.cm.,  erythrosin  solution  (1  :  500) 
2  c.cm. ;  and  of  this  mixture  1-2  c.cm.  can  be  added  to  every 
100  c.cm.  of  emulsion.  Vogel's  azaline  may  be  used  in  the  same 
proportion.  The  silver  salts  of  eosine  have  been  very  successful 
in  reproducing  mixed  colours.  Valenta  gives  the  two  following 
chloro-bromide  emulsions  as  also  giving  good  results,  particularly 

324 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pho 


with  the  less  refrangible  rays,  but  cannot  state  which  is  the 
better  : — 

I. 

A.  B. 

Water    200  c.cm.  Water    15  c.cm. 

Gelatine       ...      10  g.  Silver  nitrate ...      1-5  g. 

C. 

Water    15  c.cm. 

Potassium  bromide    0-35  g. 

Sodium  chloride    0-35 

A  is  divided  into  two  parts,  one  poured  into  B,  the  other  into 
C,  well  mixed,  and  then  B  added  toC  at  35°-4on  C. 

II. 

A. 

Water    ...       ...    300  c.cm. 

Gelatine    10  g. 

Silver  nitrate    ...       ...       6  ,, 

B. 

Water         ...       ...       ...  ...  ...  300  c.cm. 

Gelatine                          ...  ...  ...  20  g. 

Potassium  bromide   ...  ...  2-4  „ 

Sodium  chloride    ...  ...  1*5 

Mixing  temperature,  350  C. 

The  exposure  for  sunlight  for  the  bromide  plates  with  a  width  of 
0-3  to  0*5  mm.  slit  is  one  minute,  but  with  a  wide  open  slit  and 
a  condensing  lens  ten  to  twenty  seconds.  For  developing 
Valenta  used — 

A. 

Pyrogallol    4  g. 

Water      ...    400  „ 

Nitric  acid   6  drops. 

B. 

Potassium  bromide   10  g. 

Water      400  ,, 

Ammonium  sulphite    12  „ 

Ammonia  (sp.  gr.  0*91)    14  c.cm. 


Pho] 


DICTIONARY  OF  PHOTOGRAPHY. 


For  2-3  parts  of  B  are  mixed  with  1  part  of  A  and  12-14  parts 
water.  Valenta  has  also  used  the  following  modification  of 
Lumiere  s  developer : — 

A. 

Water         ...       ...       ...       ...       ...    100  c.cm. 

Pyrogallol    ...       ...       ...    1  g. 

B. 

Water                            ...       ...       ...  200  c.cm. 

Potassium  bromide   20  g. 

Ammonia  (sp.  gr.  0-96  at  180  C.)   67  c.cm. 

For  use  mix 

Solution  A   ...       ...       ...    10  c.cm. 

n       B   20  „ 

Water    70  „ 

For  chloride  bromide  plates  these  developers  should  be  diluted 
to  double  the  volume.  For  fixing,  a  4  or  5  per  cent,  solution  of 
potassium  cyanide  is  the  best.  Valenta  points  out  that  under- 
exposed and  under-developed  photochromes  thus  prepared  can 
be  intensified  with  mercuric  chloride,  followed  by  amidol  and 
sulphite.  Lippmann  presented  to  the  Academie  des  Sciences 
de  Paris  on  October  24th,  1892,  some  good  reproductions  of  the 
solar  spectrum  on  bichromated  albumen  and  gelatine  ;  these 
only  show  the  colours  when  wet.  The  albumen  must  first  be 
coagulated  with  mercuric  chloride  solution,  then  well  washed 
before  treating  with  bichromate  of  potash.  Lippmann's  theory 
of  the  formation  of  these  colours  is  that  in  the  chromated  film 
series  of  maxima  and  minima  of  interference  are  formed.  The 
maxima  alone  make  the  film  insoluble,  and  in  treating  the  plates 
with  water  a  laminar  structure  is  formed  which  is  partly  saturated 
with  water  and  partly  dry.  The  index  of  refraction  of  the  laminae 
varies  periodically  and  thus  gives  rise  to  the  interference  pheno- 
mena and  the  colours.  St.  Florent  is  stated  to  have  obtained 
photochromes  or  colour  photographs  by  treating  a  plate  coated 
with  a  thin  gelatine  film  with  a  solution  of — 

Water    1,000  c.cm. 

Ferric  chloride       ...       ...       ...       ...  log. 

Citric  acid   5  „ 

326 


DICTIONARY  OF  PHOTOGRAPHY.  [Pho 

and  then  exposing  under  a  coloured  glass  picture.  Valenta 
writes  upon  the  preparation  of  emulsions  for  Lippmann's  pro- 
cess :    "The  drawback  to  plates  prepared  by  the  Lumiere  or 
Valenta  process  for  colour  photographs  is  that  the  means  taken 
to  secure  the  grain  being  sufficiently  fine  results  in  the  plates 
being  very  slow.    So  slow  is  this  emulsion  that  a  plate  exposed 
in  a  sensitometer  for  five  minutes  to  a  light  of  fifty  candle  power 
scarcely  shows  the  first  number.    Valenta  finds,  however,  that 
the  addition  of  one  gramme  of  sodium  sulphite  to  300  c.cm.  ol 
emulsion  with  subsequent  heating  at  380   C.  results  in  five 
minutes  in  an  emulsion  showing  the  fourth  number  on  the 
sensitometer,  or  the  eighteenth  number  in  an  hour.    Krone  has 
formulated  the  following  conditions  or  rules  which  must  be 
complied  with  for  the  successful  working  of  Lippmann's  process. 
(1)  It  is  essential  that  the  sensitive  film  be  homogeneous,  and 
that  a  reflecting  surface  be  in  contact  with  the  film,  the  rays  from 
which  reflecting  surface  must  interfere  with  the  direct  rays  and 
thus  produce  stagnant  or  stationary  waves  in  the  film.    (2)  If 
the  thickness  of  the  film  exceeds  a  certain  thickness,  the  colours 
are  not  obtained,  or  not  the  correct  colours.    Where  the  regular 
film  encloses  a  particle  of  dust  this  appears  particularly  notice- 
able.    (3)  The  faithful  reproduction  and  appearance  of  the 
colours  in  correct  position  is  not  absolute,  but  depends  upon  the 
following  without  exception  : — (a)  an  absolutely  accurate  con- 
currence in  the  film  of  the  finest  divided  silver  haloid  with  the 
colour  sensitiser  and  the  correct  amount  of  the  latter  ;  (b)  on  the 
temperature  in  drying  the  film  ;  (c)  on  the  duration  of  exposure  ; 
(d)  on  the  development.    It  may  thus  happen  that  with  less 
favourable-  concurrence  of  the  above-mentioned  factors,  green 
may  appear  in  the  place  of  blue,  and  yellow  in  the  place  of  red. 
This  is  also  the  reason  why  many  appearances  of  anomalous 
colour-dispersion  appear,  and  that  many  colours  are  wanting, 
etc.    (4)  An  increased  or  diminished  dampness  of  the  results 
alters  the  colours.    (5)  The  altitude  of  the  sun  at  the  time  of  the 
exposure  has  considerable  influence  on  the  results,  as  shortly 
before  sunset  or  after  sunrise,  although  all  the  colours  may 
appear  vigorous  in  the  spectroscope,  yet  the  more  refrangible 
rays  show  much  less  actinic  power,  so  that  finally,  with  prolonged 
exposure — for  instance,  shortly  before  sunset — the  violet,  blue, 
and  ultra-violet  are  not  reproduced.    The  ultra-violet  first  dis- 

327 


Pho] 


DICTIONARY  OF  PHOTOGRAPHY. 


appears,  then  the  blue,  the  place  of  the  latter  being  taken  up  by 
a  prolongation  of  the  green,  or  shows  a  steely-grey  colour.  (6) 
With  sufficiently  long  exposure  the,  to  the  eye  invisible,  infra-red 
(beyond  the  line  A)  appears  as  a  dark  purple,  the  ultra-violet 
(beyond  H)  sinking  into  yellowish  rose-red  lavender.  (7)  In  the 
ultra-violet  (beyond  H)  there  appears,  when  an  electric  arc  light 
is  used,  a  very  intense  light  maximum  which  is  separated  from 
the  H  group  by  a  group  of  colourless  carbon  lines,  this  maximum 
being  visually  recognised,  and  with  sufficient  exposure,  is  of  a 
deeper  and  more  intense  dark  blue  than  the  indigo  blue  of  the 
solar  spectrum.  (8)  The  actinic  intensity  of  the  electric  arc  light, 
at  a  distance  of  36  cm.  from  the  slit  of  the  spectroscope  to  the 
positive  pole  of  the  carbons,  is  to  direct  sunlight  (mid-day,  April, 
clear  sky)  as  1  :  38  to  1  :  40.  (9)  Only  by  using  Lippmann's 
mercury  mirror,  when  the  requirements  of  rule  3  are  complied 
with,  is  it  possible  to  obtain  the  photographic  colour  results 
corresponding  to  the  visual  spectrum  and  the  colours  in  their 
correct  places.  Reflected  light  acts  always  more  strongly  than 
direct  light,  and  Krone  recommended  in  the  first  place  the  use  of 
a  metallic  mirror  in  order  to  avoid  the  formation  of  two  spectrum 
images  which  would  give  rise  to  the  formation  of  mixed  colours  in 


the  pictures.  Fig.  79  shows  Lippmann's  arrangement  for  obtain- 
ing a  spectrum,  l  is  an  electric  arc  lamp,  the  rays  from  which 
are  condensed  by  a  lens  upon  F  which  is  an  opaque  screen 
with  a  narrow  slit  in  it.  a  is  a  convergent  lens  which  renders 
the  rays  parallel  from  whence  they  strike  the  prisms  p,  and  are 
formed  into  an  image  by  o,  the  lens  of  the  camera  c,  on  e,  the 
dark  slide  of  particular  form.  To  view  these  photographs  in 
natural  colours  it  is  necessary  to  cement  them  to  a  prism  of  small 
angle  and  back  them  with  black  velvet  or  black  varnish.  The 
method  of  showing  them  by  artificial  light  being  sketched  in 

328 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pho 


Fig.  80. 


fig.  80,  in  which  A  is  the  lantern,  c  the  condensers,  sending  a 
beam  of  parallel  light  on  to  the  picture  whence  it  is  reflected 
and  taken  iup  by  a  projecting  lens 
and  thrown  on  the  screen.  _^=7^~7 

Heliochromy,  or  Three  Colour-sen- 
sation process.  This  is  based  upon  /  \ 
the  theory  of  colour  sensation  first  /  • 
promulgated  by  Young,  Helmholtz, 
and  Clerk  Maxwell,  which  assumes 
that,  although  we  have  six  or  seven 
spectrum  colours,  yet  our  eyes  are 
provided  with  three  nerve  fibrils, 
one  conveying  the  sensation  of  red, 
another  of  blue,  and  another  of  green, 
the  other  and  intermediate  colours 
being  excited  by  a  mixture  of  the  red, 
green,  and  blue  in  varying  propor- 
tions. The  first  suggestion  was  made  by  Collen  in  1865,  and 
practically  tried  by  Duhauron,  Cros,  and  Ransonnet,  and  later 
by  Ives,  Vogel,  Kurtz,  and  others.  The  subject  may  well  be 
divided  into  two  heads,  first,  the  production  of  lantern  slides 
or  transparencies,  and,  secondly,  the  production  of  prints.  For 
the  production  of  lantern  slides  the  process  is  by  no  means 
difficult.  We  require  three  negatives,  a  representing  the  red 
sensation,  b  the  green  sensation,  and  c  the  blue  sensation.  For 
the  red  sensation  a  red  sensitive  orthochromatic  plate  should  be 
used,  or  an  ordinary  plate  which  has  been  sensitised  by  a 
solution  of  cyanine,  one-third  of  a  grain  in  an  ounce  of  absolute 
alcohol ;  the  plate  should  be  flowed  over  with  this,  dried  in 
absolute  darkness,  then  immersed  in  distilled  water  for  two  or 
three  minutes,  and  again  dried  in  the  dark.  For  the  coloured 
screen  to  cut  off  the  blue  rays  a  piece  of  orange-red  glass  should 
be  used.  For  the  green  sensation  a  commercial  isochromatic 
plate  should  be  used,  and  two  thicknesses  of  chromium  green 
glass.  For  the  blue  sensation  an  ordinary  plate  with  two  thick- 
nesses of  cobalt  blue  glass  should  be  used.  From  these 
negatives,  lantern  slides  should  be  made  in  the  ordinary  way, 
and  projected  by  means  of  a  triple  lantern.  The  transparency 
representing  the  red  sensation  should  be  projected  through  the 
glass  used  to  take  it,  that  of  the  green  sensation  through  one 

329 


Pho]  DICTIONARY  OF  PHOTOGRAPHY. 

thickness  of  the  green  glass,  and  that  of  the  blue  sensation 
through  one  thickness  of  the  blue -violet  glass.    If  the  images 
are  accurately  superimposed,  the  result  will  be  a  reproduction  of 
the  objects  in  their  colours.     For  the  production  of  prints  a 
slightly  different  procedure  is  required.     Three  negatives  are 
obtained  in  somewhat  similar  fashion,  but  in  this  case  we  use 
red,  yellow,  and  blue  as  the  three  primary  colours.    As  in  all 
photomechanical  printing  processes,  like  collotype,  which  we  will 
take  as  an  example,  it  is  the  shadows  which  print.    If  a  collotype 
plate  is  exposed  under  a  negative,  it  will  be  found  that,  after 
washing,  only  the  shadows  or  those  portions  of  the  film  acted 
upon  by  light  will  take  the  ink,  the  high  lights  where  the  film 
was  protected  refusing  to  take  the  greasy  ink.    The  result  of 
this  is  that  we  use  that  negative  for  making  the  printing  plate,  in 
which  the  particular  colour  corresponding  to  the  ink  has  not 
acted :   for  instance,  the  collotype  plate  made  from  the  red 
negative,  or  the  negative  taken  through  the  red  screen,  is  inked 
with  blue  ink ;  the  plate  from  the  negative  taken  with  the  green 
screen  is  inked  with  red  ink ;  and  the  plate  from  the  negative 
taken  with  the  blue-violet  screen  is  inked  with  yellow.  The 
negatives  used  for  any  printing  process  must  represent  the  action 
of  two  colours,  and  represent  the  third  as  transparent :  for  instance, 
with  the  negative  taken  with  the  orange-red  screen,  the  red  and 
yellow  must  be  opaque,  but  the  blue  transparent ;  the  negative 
taken  with  the  green  screen  must  have  the  yellow  and  blue 
opaque,  but  the  red  transparent;  the  negative  taken  with  the 
blue-violet  screen  must  have  the  red  and  blue  opaque,  but  the 
yellow  transparent.     The  plates  suggested   for  lantern-slide 
making  may  be  used  again,  but  the  same  screens  will  not  do. 
Various  screens  have  been  suggested,  but  at  present  I  am  unable 
to  give  exact  directions  for  making  them.    Hruza  has  suggested 
the  use  of  cochineal  red  and  aniline  yellow,  I  :  100,  for  the 
orange-red  screen ;  for  the  green  screen  a  solution  of  malachite 
green,  I  :  200  ;  and  for  the  blue  a  solution  of  ethyl  violet,  1  :  200. 
The  disadvantage  of  using  liquids  is  that  there  is  far  greater  loss 
of  light  than  when  using  collodion  or  gelatine  dyed.    The  inks 
used  vary  slightly  according  to  the  recommendations  of  autho- 
rities, but  cadmium  or  chromium  yellow,  carmine  and  milori  or 
ultramarine  blue  may  be  taken  as  the  usual  ones.    The  yellow 
is  printed  first,  then  the  red,  and  finally  the  blue.    In  the  pro- 

330 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pho 


duction  of  prints  by  the  aid  of  process  blocks,  one  line  screens 
only  are  used  for  each  block,  the  said  lines  crossing  each  other 
at  angles  of  300.  Whilst  from  the  difficulties  of  obtaining 
perfect  printing  inks  corresponding  exactly  to  the  spectroscopic 
absorption  curves  required,  it  is  at  present  impossible  to  obtain 
an  absolutely  faithful  reproduction  of  an  artist's  sketch  or  draw- 
ing. There  is  no  difficulty  in  making  lantern  slides  of  absolutely 
faithful  accordance  with  the  original,  nor  is  the  work  beyond  the 
ordinary  scope  of  an  amateur. 

Photogravure.  A  process  of  photomechanical  printing  by 
means  of  which,  by  the  aid  of  various  light-sensitive  substances, 
copper  plates  are  obtained,  which  are  inked  and  printed  from,  the 
same  as  an  engraver's  copper  or  steel  plate.  There  are  several 
methods  of  working  it,  but  the  most  popular,  and  the  easiest  for 
an  amateur,  is  that  known  as  Klic's.  The  apparatus  necessary 
for  this  is,  first,  a  dusting  box,  which  should  be  at  least  three 
times  the  area  on  all  sides  of  the  largest  plate  to  be  coated.  This 
is  provided  with  a  narrow  door  at  one  side.  The  box  should  be 
mounted  on  trunnions  or  side  pivots,  so  as  to  swing  freely.  Raw 
Syrian  asphalt,  finely  powdered,  or  a  mixture  of  asphalt  and  resin, 
is  also  required.  Finely  polished  copper  plates  and  perchloride  of 
iron  ;  this  latter  should  be  solid,  and  not  the  acid  solution  of  the 
chemist.  The  perchloride  is  dissolved  in  water  by  adding  one- 
third  the  quantity  of  distilled  water  to  it  and  allowing  it  to  dissolve 
as  much  as  possible,  and  then  diluting  it  with  distilled  water  till 
it  marks  450  Baume,  400,  38°  350,  and  270  Baume.  These  five 
solutions  are  carefully  prepared  of  the  above  strength,  or,  in  the 
absence  of  a  hydrometer,  the  solutions  may  be  made  up  of  the 
percentage  strengths  which  correspond  to  the  above,  47,  41,  38, 
35,  and  27.  These  must  be  the  percentage  solutions,  and  can  be 
made  as  follows,  assuming  that  we  require  10  ozs.  of  solution  : — 

1.  Perchloride  of  iron,  2,256  grs.  Dist.  water  to  make  10  ozs. 

2.  „  i,968  n 

3-  n  1,824  H 

4-  n  1,680  „ 

5-  „  1,296  „   

We  require  a  transparency  of  the  negative  to  be  reproduced. 
This  transparency  should  be  made  on  an  ordinary  dry  plate,  not 
a  lantern  plate,  and  should  be  soft  and  delicate,  more  approaching 

33* 


Pho]  DICTIONARY  OF  PHOTOGRAPHY. 

the  ordinary  negative  than  lantern-slide  characters.  From  this 
transparency  we  must  prepare  a  negative  in  carbon.  Either 
transparency  or  standard  brown  may  be  used.  The  negative 
must  be  thin,  and  quite  free  from  any  deposit  in  the  deepest 
shadows.  The  dusting  box  must  be  lined  with  varnished  paper, 
and  the  asphalt  sifted  through  fine  linen.  The  copper  plates 
should  be  obtained  already  bevelled  and  polished,  and  merely 
require  cleaning  with  weak  caustic  potash  solution  and  then 
with  ammonia,  and  washing,  whitening,  rinsing  and  drying. 
The  plates  are  now  ready  for  graining.  To  do  this  the  box,  con- 
taining from  one-half  to  a  pound  of  powder,  is  rather  slowly 
revolved  for  about  three  times,  and  then  brought  to  a  stand 
with  the  door  at  the  bottom.  It  is  allowed  to  rest  for  one 
minute,  and  then  the  copper  plate,  placed  on  a  larger  piece  of 
plate-glass,  is  placed  on  a  box  or  piece  of  wood  on  the  bottom  of 
the  box  inside,  the  door  closed,  and  the  dust  allowed  to  settle  for 
about  five  minutes,  and  then  taken  out  and  examined  to  see 
whether  enough  dust  or  grain  is  on  it.  How  much  grain  to  lay 
is  a  matter  of  experience.  A  dark  subject  requires  not  only  more 
grain,  but  a  coarser  grain,  than  a  lighter  subject.  For  ordinary 
subjects  the  best  way  is  to  allow  the  dust  to  settle  for  about  one 
minute,  and  then  to  leave  the  copper  plate  in  for  ten  minutes. 
Having  grained  the  plate,  the  next  thing  is  to  fix  the  grain.  This 
is  done  by  heat,  and  the  best  heater  is  a  proper  copper  plate 
heater.  Failing  this,  an  ordinary  gas  stove  may  be  used,  or 
merely  a  sheet  of  iron  placed  over  a  gas  stove.  The  plate  is  now 
placed  on  the  hot  plate  till  the  grain  melts  and  adheres  firmly  to 
the  plate.  The  sign  of  the  grain  being  fixed  is  a  peculiar  bloom 
or  steely  colour,  which  appears,  when  looking  at  the  plate,  at  an 
angle  of  about  300.  When  the  grain  is  fixed  the  plate  should  be 
allowed  to  spontaneously  cool ;  and  in  this  condition  the  grain 
will  not  rub  off,  and  the  plate  may  be  kept  some  time.  The 
carbon  negative  is  the  next  thing  to  be  prepared,  and  this  is 
printed  in  the  usual  way,  a  safe  edge  being  used.  As  we  wish 
the  margins  to  be  white,  it  is  necessary  to  use  some  protecting 
covering ;  and  the  simplest  method  is  to  cut  a  sheet  of  orange 
paper  the  full  size  of  the  negative.  Out  of  the  middle  of  this  cut 
a  piece  the  exact  size  of  the  desired  picture,  and  from  the  margin 
cut  another  eighth  of  an  inch  all  round;  and,  after  the  real 
exposure  has  been  given,  cover  the  exposed  portion  with  the 

332 


DICTIONARY  OF  PHOTOGRAPHY.  [Pho 

central  cut-out  and  the  margin  with  the  edge.  This  is  best  done 
by  pasting  the  mask  and  margin  on  a  piece  of  glass  the  exact 
size  of  the  negative.  This  ensures  an  insoluble  strip  of  carbon 
tissue  all  round  the  picture.  The  carbon  negative  is  now  deve- 
loped on  the  copper  plate  in  the  usual  way,  and  when  developed 
and  fixed  is  rinsed  with  water,  then  with  a  mixture  of  equal 
parts  of  methylated  spirit  and  water,  and  finally  with  spirit 
alone  till  all  the  water  is  out  of  the  film.  The  plate,  both 
margins  and  back,  is  covered  with  black  varnish,  allowed  to  dry, 
and  it  is  ready  for  etching.  The  plate  is  now  placed  in  No.  I 
bath  of  perchloride,  and  left  for  one  minute  ;  then  into  No.  2, 
where  it  is  left  for  two  or  three  minutes ;  then  into  No.  3  for 
about  three  minutes ;  then  into  No.  4  for  three  minutes  ;  and, 
finally,  into  No.  5  till  the  highest  lights  on  the  copper  are  just 
darkened,  and  half  a  minute  longer.  The  plate  is  now  dropped 
into  a  5  per  cent,  solution  of  caustic  potash,  the  resist  or  carbon 
cleared  off,  and  then  the  varnish,  with  turpentine  and  benzole, 
the  plate  well  washed  and  polished  with  whitening,  when  it  is 
ready  for  printing  from  in  the  copperplate  press. 

Photo-Lithography.  One  of  the  most  important  of  all 
photo-mechanical  methods  in  which  a  print  is  obtained  from  a 
negative  and  transferred  to  lithographic  stone,  and  printed  from 
in  the  ordinary  way. 

Photometer.  Literally  a  measurer  of  light.  It  has  lately 
been  much  recommended  for  calculating  the  exposure  for  the 
sensitive  plates  ;  but  as  the  action  of  these  is  solely  to  measure 
the  visual  rays,  and  as  the  latest  image  is  imprinted  on  the  plate 
by  the  chemical  and  not  the  visual  rays,  it  is  obviously  unfair  to 
judge  of  the  exposure  to  the  one  by  the  intensity  of  the  other. 

Photo-Micrography.  The  art  of  obtaining  photographic  en- 
largements of  microscopic  objects  by  the  aid  of  the  microscope. 
The  chief  advantage  of  photo-micrography  is  that  the  results 
obtained  are  free  from  much  of  the  personal  element  which  is 
always  present  with  hand-drawn  diagrams.  And  again,  although 
the  successful  results  are  often  extremely  difficult  and  tedious  to 
obtain,  yet  when  obtained  they  are  far  superior  to  anything  that 
can  be  done  by  hand,  and  actually,  the  author  thinks,  not  so 
tiring  as  having  to  pore  for  some  hours  over  a  microscope  with 
pen  and  pencil,  and  laboriously  trace  the  minute  details  of  some 

333 


Pho] 


DICTIONARY  OF  PHOTOGRAPHY. 


pathological  or  histological  subject,  which  was  for  many  months 
the  author's  work  :  this,  unfortunately,  before  a  practical  know- 
ledge of  photography  was  obtained.    Only  the  bare  details  of 
this  art  can  be  entered  upon.    For  fuller  detailed  instruction  the 
operator  must  refer  to  the  special  handbooks,  such  as  that  of 
Charters   White,  Jennings,    Dr.   Sternberg,   Andrew  Pringle, 
Bousfield,  the  monthly  Microscopical  Journal,  "The  Transactions 
of  the  Royal  Microscopical  Society,"- etc.    Any  good  firm  micros- 
cope stand  may  be  employed,  and  the  draw-tube  should  be  lined 
with  black  velvet  or  cloth — not  the  usual  black  matt  varnish, 
which  soon  wears  off.     Caution  must  be  exercised,  however, 
that  the  foreign  makes  with  somewhat  narrow  draw-tubes  are 
not  obtained,  as  these  limit  the  field  of  view  very  much.  A 
mechanical  stage  is  almost  a  necessity.     Several  lenses  will 
be  required,  and  these  should  be  of  low  or  narrow-angle,  and 
usually  a  2-,  I-,  \-,  and  |-in.  will  be  found  sufficient,  and  a  ^-in. 
wide-angle  also.  These  should  be  obtained  from  English  makers 
who  now  manufacture  lenses  specially  for  photo-micrography, 
A  large  bull's-eye  condenser  and  a  parabolic  reflector  are  also 
required.    The  majority  of  beginners  will  most  likely  confine 
themselves  to  small  plates,  the  lantern  size  3^  x  3^  being  the 
most  usual.    Special  forms  of  light  cameras  are  now  made  for 
this  size  for  use  with  the  eye-piece,  and  from  practical  ex- 
perience the  beginner  is  recommended  to  always  use  the  eye- 
piece till  he  has  become  more  proficient.    The  camera,  however, 
must  have  a  sufficient  pull  of  bellows,  about  12  or  14  inches.  For 
focussing,  the  usual  ground  glass  is  utterly  useless,  the  only 
method  being  to  use  a  piece  of  patent  plate  which  has  lines 
drawn  upon  one  surface  with  a  diamond;  and  when  these  lines  and 
the  image  are  both  in  focus  with  a  compound  focusser,  the  correct 
focus  is  obtained.    Or  another  method  consists  of  moving  the 
head  from  side  to  side,  and  when  the  image  moves  with  the  head 
the  object  is  not  in  focus  ;  when,  however,  it  remains  stationary 
the  focus  is  correct.  The  method  of  attachment  of  the  microscope 
to  the  camera  differs  with  every  operator, — some  employ  loosely 
fitting  black  velvet  sleeves ;  others  employ  a  brass  connection, 
into  which  the  microscope  tube  either  screws  or  merely  slides. 
The  question  as  to  the  best  plates  to  use  can  only  be  answered 
to  some  extent  by  asking  what  is  going  to  be  photographed, 
as  the  plates  must  be  suited  for  the  subject;  preparations  of 

334 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pin 


objects  stained  with  the  various  dyes  usually  used  require  dif- 
ferent plates.  In  some  cases,  especially  those  in  which  yellow 
predominates,  isochromatic  plates  will  be  found  the  best.  In 
others,  where  orange  or  orange-red  is  the  prevailing  colour,  then 
plates  specially  sensitised  for  these  rays  will  be  found  most 
effectual.  If  the  illuminant  used  is  gas  or  lamp  light,  then  the 
exposure  may  be  considerably  shortened  by  always  using  iso- 
chromatic plates  as  these  plates  are  much  more  sensitive  to  such 
light  than  ordinary  plates.  The  rapidity  of  the  plate  is  not  a 
subject  of  much  consequence,  as  equally  good  results  have  been 
obtained  by  eminent  workers  on  both  slow  and  rapid  makes. 

Phototype.  A  mechanical  printing  process  in  which  a  gelatine 
film  itself  is  used  to  print  from. 

Pinholes.  Minute  transparent  spots  making  their  appear- 
ance on  the  plate  in  the  fixing  bath.  They  are  chiefly  due  to  air 
bubbles,  or  particles  of  dust  adhering  to  the  film  whilst  in  the 
developer,  and  thus  preventing  the  action  of  the  developer  on 
the  film  at  these  spots.  To  obviate  these  the  film  should  be 
brushed  with  a  soft  camel's-hair  brush  whilst  in  the  developer, 
but  where  pinholes  are  in  existence  recourse  must  be  had  to 
retouching  or  painting  them  out  with  some  non-actinic  colour. 

Pinhole  Photography.  Of  late  years  the  possibility  of  taking 
passable  negatives  without  the  use  of  an  ordinary  camera  and 
lens  has  become  an  established  fact.  For  this  purpose  any 
rectangular  box  which  is  absolutely  light-tight  will  do.  In  one 
end  make  a  minute  hole  with  the  point  of  a  needle,  and  at  the 
other  end  place  the  sensitive  plate,  keeping  it  in  its  place  by 
means  of  a  clip  or  other  simple  arrangement.  A  prolonged 
exposure  is  required,  about  twenty  or  thirty  times  the  ordinary  one 
for  any  given  subject.  No  focussing  is  required,  as  the  image  is 
always  fairly  sharp,  no  matter  what  distance  the  plate  is  from 
the  hole.  The  larger  the  plate  the  wider  the  angle,  and  the 
greater  the  distance  the  larger  the  image.  As  an  experiment,  it 
should  be  tried  by  every  amateur,  as  the  materials  are  always  at 
his  command  in  the  shape  of  an  empty  plate-box.  There  is 
with  every  different  aperture  a  correct  position  for  the  sensitive 
surface  which  gives  the  maximum  of  sharpness,  and  this  can  be 
found  by  Abney's  formula.     Mr.  Alfred  Watkins  has  calculated 

335 


Piz] 


DICTIONARY  OF  PHOTOGRAPHY. 


out  a  table  on  the  above  formula,  and  suggests  that,  as  ordinary 
sewing  needles  are  made  to  standard  sizes,  they  should  be  used 
to  punch  the  holes  in  the  metal  plate  or  card. 


No.  of  Needle. 

Diameter. 

Distance  to  Plate. 

Ratio. 

Calculate  as 

! 

2V  inch 

32  inches 

1 

7inr 

fl7o 

2 

1 1 

■?"3  » 

28  „ 

1 

^475" 

fH 

3 

■h  » 

23  M 

f/60 

4 

20  „ 

1 

6  SO 

5 

1 

a  1  » 

15  » 

T5"6~ 

6 

» 

13  » 

1 

44"0" 

fM 

7 

1 

liTT  M 

IO  „ 

1 

TJ9IT 

f/39 

8 

4V  }) 

8  „ 

MS 

9 

1 

4  9  »» 

6  „ 

1 

f!*9 

10 

1 

Si  »> 

5  r, 

1 

fl*7 

and  multiply  by  100. 

Pizzighelli's  Printing-out  Process.  Rives  or  Saxe  paper 
may  be  used,  either  glossy  or  with  matt  surface.  The  following 
solutions  are  required  : — 

No.  1  Solution,  Gum  Arabic. 

Gum  arabic  (finest  white  lumps)  770  grs.  or  50  grms. 
Distilled  water   27  drms.  ,,  150  c. cm. 

No.  2  Solution  Arrowroot. 

Arrowroot  ...       ...       ...      30  grs.    or     2  grms. 

Distilled  water   27  drms.  ,,   150  c. cm. 

Mix  the  arrowroot  into  a  paste  with  a  little  water,  add  to  the 
remainder  of  distilled  water  whilst  boiling,  and  keep  the  tempera- 
ture up  for  five  or  ten  minutes.  No.  1  solution  gives  the  best 
effects. 

336 


DICTIONARY  OF  PHOTOGRAPHY 


[Piz 


No.  3  Solution,  Ammonia  Ferric  Oxalate. 

Ferric  oxalate    308  grs.     or  20  grms. 

Oxalic  acid        ...       ...       ...       8    „  0.5  grm. 

Ammonium  oxalate  ...  288  or  308  or  18  to  20  grms. 
Distilled  water   27  drms.  or  150  c.cm. 

No.  4  Solution,  Sodium  Ferric  Oxalate. 

Ferric  oxalate     ...    308  grs.    or  20  grms. 

Oxalic  acid    ...       8    ,,      ,,  0  5  grm. 

Sodium  oxalate  ...       ...    230  to  290    ,,  or  50  to  60  grs. 

Distilled  water   27  drms.  or  150  c.cm. 

The  exact  amount  of  sodium  or  ammonium  oxalate  to  use  is 
found  by  the  formation  of  a  brilliant  emerald  green  colour, 
turning  slightly  darker  as  more  of  the  salt  is  added.  The  addi- 
tion of  the  salt  must  be  stopped  at  this  stage.  After  shaking 
slightly,  filter  the  solutions,  and  preserve  from  actinic  light. 

No.  5,  Sensitising  Liquid. 
Solution   of  chloro-platinite  of 

potash  (1  in  6)       ...    408  mins.  or  50  c.cm. 

No.  I    391    „      „  49  „ 

m  3    374    m      m  48  m 

Or  No.  6. 

Solution   of  chloro-platinite  of 

potash  (1  in  6)       ...     24  mins.  or  50  c.cm. 

11  4   39i    n     11  49 

.1   1    374    n     ii  48  11 

Or  No.  7. 

Chloro-platinite  of  potash       ...  24  grs.  or  1*5  grms. 

Sodium  oxalate   ...  24   „  ,,  1*5 

Ferric  oxalate    31    ,,  „      2  ,, 

Oxalic  acid        ...       ...       ...        3  grs.  or  0-3  grm 

Gum  arabic       ...    52   ,,  ,,    4  c.cm. 

Distilled  water,  to  make         ...  480  mins.  „  25 

The  mixtures  are  well  stirred,  filtered  through  muslin,  and 
kept  from  actinic  light.    No.  5  gives  bluish  black,  No.  6  brownish 

337  z 


Pla] 


DICTIONARY  OF  PHOTOGRAPHY. 


black  tones.  The  coating,  drying,  and  storing  of  the  paper  are 
precisely  the  same  as  for  the  original  process  patented  by 
Willis.  Chlorate  of  potash  may  be  added  in  the  same  way,  to 
increase  contrast.  About  90  minims  of  sensitising  liquid  are 
required  for  a  sheet  10  by  8.  The  printing  may  be  carried  on 
until  the  image  has  appeared  in  all  its  parts,  and  should  be  no 
darker  when  printed  than  required.  When  finished,  the  print  is 
washed  in  acidified  water,  as  recommended  for  the  old  process) 
and  finished  in  the  ordinary  way.  A  second  method  of  printing 
is  to  print  till  the  general  details  are  out,  but  all  the  half-tones 
are  wanting.  The  print  is  then  taken  from  the  frame  and  put  on 
one  side,  when  the  action  set  up  by  the  light  continues,  and  in 
from  a  half  to  two  hours  the  print  is  finished,  and  can  be  treated 
as  above  in  acidified  water,  or  the  incomplete  picture  may  be 
developed  upon  a  cold  dilute  solution  of  carbonate  of  soda  of  the 
following  strength  : — 

Carbonate  of  soda    38  grs.    or     2  grms. 

Distilled  water   27  drms.      150  c.cm. 

Immerse  the  print  in  this  till  sufficiently  developed.  A  third 
method  of  printing  is  to  expose  till  only  the  principal  details  are 
visible,  and  develop,  as  in  the  old  process,  upon  a  hot  solution  of 
potassium  oxalate. 

Platinotype.  The  process  was  first  invented  by  Mr.  W. 
Willis,  and  the  right  for  the  sale  of  the  paper  and  materials  for 
making  it  rests  solely  in  a  company  formed  by  him.  The  basis 
on  which  this  process  is  founded  is  the  reduction  of  ferric  oxalate 
by  the  action  of  light  into  ferrous  oxalate,  and  the  reduction  of  a 
platinum  salt  by  the  ferrous  oxalate  in  the  metallic  state,  when 
wetted  with  a  suitable  agent.  The  following  is  stated  by  Berkely 
to  be  the  action  that  takes  place  : — 

Fe2(C204)3    =      2FeCA,      +  2C02 

Ferric  oxalate  =  Ferrous  oxalate  +  Carbonic  acid  gas 

6Fe(C204)  +        3K2PtCl4       =  2Fe(C204)3  +  Fe2C16 

Ferrous      Chloro-platinite       Ferric  Ferric 

4-  =  4- 

oxalate       of  potassium         oxalate  chloride 

•    +     6KC1  +  3Pt 

+  Potassium  +  Platinum. 

chloride 

338 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pla 


The  following  are  concise  directions  for  the  process : — Paper  of 
good  strong  quality,  even  in  texture  and  white  in  colour,  should 
be  chosen,  and  may  be  sized  in  one  of  the  following  baths : — 
Soak  150  grs.  of  Nelson's  X  opaque  gelatine  in  30  ozs.  of  water 
for  half  an  hour,  and  heat  in  a  water  bath  at  a  temperature 
of  1400  F.  to  dissolve  it.  Add  45  grs.  of  powdered  alum  and 
7  ozs.  methylated  spirit,  filter  through  muslin,  and  put  in  large 
flat  dish.  Thoroughly  immerse  the  paper  bodily  in  this  solution, 
taking  care  to  break  all  adherent  bubbles ;  the  paper  should  be 
allowed  to  soak  for  three  minutes,  and  then  hung  up  by  clips  to 
dry.  The  drying  should  be  as  rapid  as  possible,  and  a  second 
bath  for  the  same  time  should  be  given,  and  the  paper  hung  up 
by  the  opposite  corners.  A  sizing  of  gelatine  tends  to  a  bluish 
black  tone ;  arrowroot  and  starch  to  a  brownish  tinge.  If  arrow- 
root or  starch  be  used,  the  following  bath  may  be  prepared : — 
Rub  150  grs.  of  arrowroot  or  pure  starch  powder  into  a  cream 
with  a  little  water,  and  then  pour  gradually  and  with  constant 
stirring  into  30  ozs.  of  boiling  water,  and  boil  for  ten  minutes ; 
then  add  7  ozs.  methylated  spirit,  and  allow  to  cool.  The  fol- 
lowing are  Pizzighelli  and  Hiibl's  formulae  for  sensitising  the 
paper : — 

Solution  of  Ferric  Oxalate. 

Ferric  oxalate    ...       ...       ...    120  grs.  or   8  grms. 

Distilled  water  ...    1  oz.    „  25  c.cm. 

Oxalic  acid        ...       ...       ...       8  grs.  ,,  0-5  grm. 

No  actinic  light  must  be  allowed  to  gain  access  to  this  solution, 
or  the  ferric  will  be  reduced  to  ferrous  salt. 

Solution  for  Increasing  Contrast. 

Solution  of  ferric  oxalate  ...  1  oz.  or  25  c.cm. 
Chlorate  of  potash       ...       ...       2  grs.  ,,o.igrm. 

The  same  care  must  be  exercised  in  the  keeping  of  this  as  of  the 
former  solution 

Solution  of  Chloro-Platinite  of  Potassium. 

Chloro-platinite  of  potassium  ...  80  grs.  or  5  grms. 
Distilled  water   ...       1  oz.   ,,  25  c.cm. 

339 


Pla] 


DICTIONARY  OF  PHOTOGRAPHY. 


Sensitising  Solutions. 
Na  i> 

Sol.  chloro-plat.  of  potassium  ...     24  drms.  or  75  c.cm. 
ferric  oxalate        ...       ...     22     „     ,,  69  ,, 

Distilled  water   4  „  14  „ 

A  normal  solution,  working  well  and  giving  deep  blacks. 

No.  2. 

Sol.  chloro-plat.  potass   24  drms.  or  75  c.cm. 

„   ferric  oxalate   18  ,,50  „ 

Sol.  chlorate  potash  (contrast  sol.)  4  „  „  14  ,, 
Distilled  water   4     „      ,,  14  „ 

This  gives  brilliant  prints. 

No.  3 

Sol.  chloro-plat.  potass....       ...     24  drms.  or    75  c.cm. 

„   pot.  chlor.  (contrast  sol.)  ...       4     ,,      „  12  5  ,, 
Distilled  water   4  I2'5  » 

This  is  a  solution  for  weak  negatives.  Chloro-platinite  of  potash 
when  obtained  commercially  should  be  tested  as  follows : — 
(1)  1  drm.  of  the  salt  should  be  soluble  in  6  drms.  of  distilled 
water.  (2)  The  solution  should  not  be  acid.  This  solution 
will  keep  unaltered  by  light  for  an  almost  indefinite  period. 
Very  feeble  light  must  be  used  for  coating  the  paper.  To  keep 
the  paper  flat  whilst  coating,  the  edges  should  be  turned  under- 
neath a  plate  of  glass  placed  upon  a  table ;  for  larger  pieces  the 
paper  can  be  easily  clipped  to  glass  plate  by  wooden  clips,  or  it 
can  be  pinned  at  the  corners  by  drawing  pins.  For  coating  a 
sheet  of  paper  8  by  10  ins.,  30  minims  of  sensitiser  are  required, 
which  should  be  poured  into  the  middle  of  paper  and  spread 
over  the  surface  with  a  uniform  circular  motion,  by  means  of  a 
pad  composed  of  a  tuft  of  cotton-wool  enclosed  in  a  piece  of  fine 
washed  muslin.  The  rubbing  should  be  continued  gently  for  at 
least  three  or  four  minutes.  As  soon  as  coated,  the  sheet  should 
be  hung  up  by  two  corners  to  dry,  and  as  soon  as  the  surface 
moisture  has  disappeared,  the  paper  should  be  carefully  and 
quickly  dried  over  a  gas  burner,  or  before  a  stove  or  fire.  The 
whole  success  of  the  process  lies  in  this  stage — the  drying  of  the 

340 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pla 


paper ;  the  paper  must  be  absolutely  dry.  This  point  is  known 
from  the  change  in  colour  from  lemon  to  an  orange  colour,  and 
by  the  crackle  of  the  paper.  Care  should  be  taken  not  to  scorch 
the  paper,  or  fog  will  be  the  result.  Between  the  coating  and 
drying  about  five  minutes  must  be  allowed  to  elapse  in  summer 
and  eight  or  nine  minutes  in  winter.  The  exposure  required  for 
the  paper  is  about  one-third  of  that  required  for  a  silver  print  from 
the  same  negative.  Absolute  dryness,  both  in  the  keeping  before, 
during,  and  after  exposure  is  a  sine  qua  ?wn  ;  the  slightest  trace 
of  moisture  immediately  renders  the  paper  useless.  It  should 
be  stored  in  tubes  in  which  chloride  of  calcium  (anhydrous)  is 
kept  to  absorb  the  moisture.  The  image  on  the  paper  is  but 
faintly  visible,  and  requires  a  developer  to  bring  it  out  in  all  its 
beauty.    This  is  made  as  follows : — 

Oxalate  of  potash    130  grs.  or  7-5  grms. 

Distilled  water   1  oz.    ,,    25  c.cm. 

This  solution  may  be  kept  as  a  stock  solution,  and  when 
required  for  use  must  be  heated  to  a  temperature  of  1700  to 
1800  F.  Development  is  effected  by  passing  the  print  face 
downwards  over  the  surface  of  the  solution,  and  allowing  it  to 
remain  for  two  or  three  seconds;  the  developed  print  should 
be  passed  at  once  into  a  bath  of  hydrochloric  acid  1  oz.,  water 
6oozs.,  and  allowed  to  remain  for  ten  minutes ;  it  should  be  then 
passed  into  another  bath  for  the  same  period,  and  lastly  into  a 
third ;  it  can  be  then  washed,  dried,  and  mounted  in  the  usual 
way.  The  developing  solution  may  be  used  over  and  over  again. 
For  over-exposed  prints  solution  at  ioo°  F.  can  be  used;  for 
under-exposed  over  i8o°F.  may  be  used  with  advantage. 

Warm  Tones  with  Platinum  Prints.  The  Platinotype  Com- 
pany issue  a  paper  which  gives  a  sepia  tinge,  which  perhaps 
owes  its  colour  to  mercuric  and  cupric  chlorides.  The  addition 
of  a  few  drops  of  solution  of  these  chlorides  to  the  developer 
materially  alters  the  colour  of  the  image.  Warmer  tones  may 
be  obtained  by  the  following  process.  The  following  solutions 
are  required : — 

Solution  No.  1. 
Oxalate  of  potash        ...       ...    463  grs.    or   25  grms. 

Oxalic  acid    ...      15    ,,      „      1  grm. 

Distilled  water  ...       ....       ...      27  drms.      100  c.cm. 

341 


Pla] 


DICTIONARY  OF  PHOTOGRAPHY. 


Dissolve  and  add 

Solution  No.  2   ...       ...       ...       3  drms.  or   10  c.cm. 

Shake  thoroughly,  and  leave;  if  crystals  form  they  are  of  no 
consequence. 

Solution  No.  2. 
A. 

Chloride  of  calcium,  crystal  ...  147  grs.  or  10  grms. 
Distilled  water   ...       2  ozs.  ,,  60  c.cm. 

Dissolve. 

B. 

Sulphate  of  copper,  crystal     ...  249  grs.     or  15  grms. 

Distilled  water  ...       ...       ...  10  drms.  ,,  36  c.cm. 

Dissolve.  Mix  A  and  B,  filter,  and  label  "Cupric  Chloride  Solu- 
tion, No.  2."  Put  solution  No.  1  into  an  iron  enamelled  dish, 
and  heat  to  1800  F.,  then  develop  the  prints  as  usual ;  wash  in 
acidified  water  (the  tint  can  be  altered  by  raising  or  lowering 
the  temperature).  Prints  that  are  already  developed  may  be 
treated  in  the  same  way.  After  washing,  the  prints  are  soaked 
for  a  short  time  in  a  5  per  cent,  solution  of  ferrous  sulphate, 
acidulated  with  a  drop  or  two  of  sulphuric  acid,  then  rinsed  in 
acidified  water  and  dried.  In  1888  a  modification  of  the  above 
process  was  suggested  by  Willis,  in  which  the  heating  of  the 
developer  is  entirely  done  away  with,  and  greater  transparency 
in  the  shadows  and  more  control  over  results  can  be  obtained. 
The  paper  has  to  be  preserved  with  the  same  care  from  damp, 
and  the  image  is  printed  rather  deeper  than  with  the  old  paper. 
It  can  be  developed  upon  the  solution  of  the  developing  salts  of 
the  manufacturers,  or  upon  the  normal  oxalate  solution  as  used 
for  ferrous  oxalate  developer.  The  print  is  floated  on  this,  and 
as  soon  as  intense  enough  washed  in  the  acid  baths  in  the  usual 
way.  Considerable  control  over  results  may  be  obtained  by  the 
use  of  glycerine  in  the  following  manner.  Three  solutions  should 
be  prepared : — 

No.  1. 

Solution  of  oxalate  of  potash   2  parts. 

Pure  glycerine  2  „ 

342 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pla 


No.  2. 

Solution  of  oxalate  of  potash   I  part. 

Pure  glycerine    ...    4  parts. 

No.  3. 

Pure  glycerine. 

The  print  should  be  pinned  to  a  board  and  a  small  pool  of  the  pure 
glycerine  poured  on  to  the  print  and  evenly  distributed  all  over 
it  by  means  of  a  soft  pad  of  linen.  If  there  are  any  portions  of 
the  print  which  have  a  tendency  to  appear  too  white,  or  wanting 
in  detail,  a  broad  mop  or  flat  brush  charged  with  solution  No.  2 
should  be  applied  to  those  places,  and  then  gradually  over  the 
whole  of  the  print,  except  in  the  very  deepest  shadows,  which 
should  be  left  untouched.  As  soon  as  the  image  begins  to 
develop,  the  brush  should  be  charged  with  No.  1  solution,  and 
passed  rapidly  and  evenly  over  the  whole  print ;  the  print  will 
gradually  gain  in  intensity,  and  by  careful  use  of  solutions 
No.  1  and  3  with  brushes,  it  will  be  possible  to  hold  back  one 
portion*. and  coax  another  out.  As  with  most  other  processes, 
success  is  not  always  attained  at  first,  and  it  may  happen  that 
our  finished  prints  are  too  dark  or  too  light.  In  the  former  case 
there  is  not  much  to  be  done,  as  platinum  is  one  of  those  intract- 
able metals  not  easily  amenable  to  reagents ;  strong  chlorine 
water  will  reduce  the  image  slightly.  Platinotype  prints  can  be 
far  more  easily  intensified,  and  several  processes  have  been 
suggested  for  this  purpose,  by  means  of  which  also  various 
modifications  of  tone  are  possible.  Dollond  suggests  what  is 
practically  a  gold  toning  process  what  he  describes  as  follows. 
The  solutions  required  are  : — 

1.  Gold  chloride         ...       ...       ...       ...    15  gr. 

Distilled  water   *]\  drachms. 

Neutralised  with  chalk,  filtered,  and  one  drop  of  strong  hydro- 
chloric acid  added. 


2.  Glycerine, 

3.  Sodium  sulphite   

Water  to   

Metol   

4.  Potassium  carbonate 
Ware  to 

343 


1  oz. 
10  „ 
5o  gr. 

I  oz. 
10  ,, 


Pla]  -  DICTIONARY  OF  PHOTOGRAPHY. 

The  following  is  the  method  of  application  : — The  platinotype 
print  developed,  cleared  and  dried  in  the  usual  way,  is  soaked 
for  two  or  three  minutes  in  water,  then  laid  upon  a  flat  surface, 
preferably  a  sheet  of  opal  glass,  and  blotted  to  remove  the  excess 
of  water.    Next  glycerine  is  gently  spread  over  the  whole  surface 
of  the  print  with  a  soft  brush  or  the  finger-tip.    When  evenly 
coated,  a  few  minims  of  the  gold  solution  are  dropped  on  and 
rapidly  mixed  with  the  glycerine  with  a  soft  camel-hair  brush. 
Very  soon  the  print  will  begin  to  gain  in  strength  and  assume  the 
blue-black  colour.    During  the  whole  time  the  toning  is  proceed- 
ing, the  surface  of  the  print  should  be  brushed  lightly  and 
quickly,  in  order  to  insure  even  action  and  to  constantly  bring 
fresh  gold  chloride  into  contact  with  the  platinum  image  ;  also 
there  seems  to  be  less  tendency  for  a  deposit  to  be  formed  on 
the  high  lights  if  the  solution  is  kept  in  motion.    The  high  lights 
should  be  watched,  and  as  long  as  they  remain  clear  the  action 
may  be  allowed  to  continue.     When  the  desired  effect  is 
obtained  or  when  any  coloration  is  seen  in  the  high  lights,  the 
print  should  be  quickly  rinsed  to  remove  the  adhering  glycerine 
and  gold.    After  this  a  mixture  of  equal  parts  of  metol  and 
potash  solutions  is  sponged  over  both  front  and  back  of  the  print. 
Washing  for  half  an  hour  completes  the  operation.    Prints  may 
be  kept  after  development  for  some  weeks,  or  even  months, 
before  toning,  but  very  old  prints  will  not  readily  tone.    If  the 
weather  is  cold,  the  water  and  dishes  used  will  probably  require 
to  be  slightly  warmed  or  the  action  will  be  very  slow.  Prints 
are  best  toned  in  good  daylight,  as  it  is  easier  to  see  that  the 
gold  is  kept  evenly  distributed  over  the  print,  and  daylight  also 
assists  the  action  and  renders  the  process  more  rapid  than  when 
performed  by  gaslight.    The  general  effect  of  the  toning  action 
is  to  slightly  increase  the  contrasts  in  the  print,  as  proportion- 
ately more  gold  is  deposited  where  there  is  a  large  quantity  of 
platinum  present  than  where  there  is  a  small  quantity.  The 
best  results  are  obtained  when  the  actual  increase  in  intensity 
required  is  small  only.     The  method  of  treatment  I  have 
described  will,  I  think,  be  found  to  have  four  distinct  uses:  (i) 
To  strengthen  under-exposed  prints  ;  (2)  To  convert  a  rusty  or 
brownish  colour  in  a  print  into  a  pure  black  ;  (3)  To  produce 
blue-black  in  the  place  of  black  prints  when  this  modification 
of  colour  is  considered  desirable ;  (4)  To  enable  brighter  prints 

344 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pla 


to  be  obtained  from  flat  negatives  than  is  usually  possible  by 
the  ordinary  method."  A  method  of  intensifying  platinotype  with 
silver  has  also  been  suggested.  For  this  either  an  acid  pyro  or 
acid  hydroquinone  developer  could  be  used,  to  which  a  few  drops 
of  a  10  per  cent,  solution  of  silver  nitrate  had  been  added.  The 
solutions  required  are, 

i.  Pyrogalloi   2  grs. 

Citric  acid  20  grs. 

Distilled  water      ...    1  oz. 


2.  Hydroquinone       ...       ...    2  grs. 

Citric  acid   ...    ...    20  grs. 

Distilled  water    1  oz. 

3.  Silver  nitrate   48  grs. 

Distilled  water    1  oz. 

The  prints  after  clearing  must  be  thoroughly  freed  from  acid 
and  placed  in  a  clean  dish.  Ten  drops  of  No.  3,  should  be  added 
to  one  oz.  of  either  1  or  2,  and  the  solution,  which  turns  white 
and  cloudy  immediately  applied  to  the  print  and  the  dish  rocked. 
As  soon  as  the  desired  degree  of  intensification  is  reached  the 
print  should  be  thoroughly  washed  and  then  fixed  in  hypo,  and 
well  washed  to  free  it  from  any  soluble  silver  salt.  The 
intensified  print  can  afterwards  be  toned  with  gold  or  platinum 
to  obtain  different  tones.  Platinotypes  may  also  be  toned  with 
uranium  by  the  following  process  suggested  by  Hubl :  — 


Uranium  nitrate    48  grs.  or   10  parts. 

Glacial  acetic  acid   48  grs.  „    10  „ 

Water    1  oz.  „  100  „ 

B. 

Potassium  ferridcyanide    ...  48  grs.  or   10  parts. 

Water        ...    1  oz.  ,,  100 

C. 

Ammonium  sulphocyanide  240  grs.  or  50  parts. 

Water    1  oz.    „  100  „ 

345 


Pla] 


DICTIONARY  OF  PHOTOGRAPHY. 


For  use,  add  to  1,000  parts  of  water  10  parts  of  the  above  solu- 
tions one  after  the  other.  The  well-washed  platinum  print 
should  be  placed  in  a  dish  and  covered  with  the  solution,  and  the 
dish  rocked  till  the  desired  tone  is  attained.  The  toning  bath 
should  then  be  poured  away,  the  prints  washed  in  frequently 
changed  water.  The  process  of  toning  is  complete  in  about  five 
minutes,  and  with  concentrated  baths  takes  place  so  quickly  that 
it  is  impossible  to  avoid  failure.  In  place  of  the  sulphocyanide, 
sodium  sulphite  may  be  used,  but  as  this  acts  more  energetically 
the  bath  must  be  more  dilute.  For  this  should  be  used  5  parts 
of  A  and  B  and  5  parts  of  a  10  per  cent,  solution  of  sodium 
sulphite  to  100  parts  of  water.  Grape  sugar  acts  very  slowly, 
and  thiosinamin  very  quickly.  Platinotypes  may  be  toned  in  a 
similar  manner  to  the  above,  with  ferridcyanide  of  iron,  and  blue 
tones  be  obtained  which  are  suitable  for  moonlight  and  night 
scenes.  With  this  process  sodium  sulphite  is  less  suitable.  The 
following  solutions  should  be  used  : 

A. 

Ammonium  iron  alum       ..  48  grs.  or      10  parts. 

Hydrochloric  acid   ...       ...  48  grs.  or      10  ,, 

Water         ..,       ...       ...  10  oz.    ,,   1,000  ,, 

B. 

Potassium  ferridcyanide    ...    10  per  cent,  solution. 
C. 

Ammonium  sulphocyanide       50  per  cent,  solution. 

For  the  toning  bath,  to  1,000  parts  of  water  add  first  5  parts  of 
A,  then  2  parts  of  B,  and  5  parts  of  C.  The  solution  should  be 
of  a  red  colour,  and  is  used  similar  to  the  above-mentioned 
uranium  bath.  The  above  physical  uranium  and  iron  toning  is 
very  easily  carried  out,  and  the  desired  tones  may  be  obtained. 
In  preparing  the  pictures,  however,  it  must  be  remembered  that 
these  baths  have  an  intensifying  action.  The  prints  before 
toning  should  have  soft  delicate  half-tones,  pure  whites,  and 
not  too  deep  shadows  ;  in  no  case  should  they  be  too  brilliant, 
otherwise  after  toning  they  will  be  hard.  Soft,  harmonious,  and 
somewhat  thin  negatives  on  soft-printing  platinotype  paper  are 
the  most  suitable.    If  the  toning  process  is  a  failure,  or  the 

346 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pla 


desired  tone  is  not  obtained,  the  prints  may  be  restored  to  their 
original  condition  by  treatment  with  dilute  ammonia.  Any 
slight  yellow  stain  may  then  be  removed  by  dilute  hydrochloric 
acid.  The  ferrocyanide  compounds  of  iron  and  uranium  with- 
stand the  action  of  acids,  but  are  removed  by  alkalies  ;  therefore 
the  toning  bath  must  be  faintly  acid,  and  the  washing  of  the 
toned  prints  must  not  be  done  by  ordinary  water  containing  lime 
or  alkalies.  It  is  in  any  case  advisable  to  add  a  few  drops  of 
acetic  acid  to  the  washing  waters  to  prevent  the  removal  of  the 
toning. 

Platino-Uranotype,  Mercuro-Uranotype,  Palladiotype. 

Under  these  names  Mr.  Alleyne  Reynolds  has  given  some 
account  of  the  result  of  his  experiments,  which  may  possibly  be 
of  some  use  in  the  future  as  printing  processes. 

Formula  for  Platino-Uranotype. 
Solution  A. 
Saturated  solution  of  uranium  chloride. 

Solution  B. 

Chloro-platinite  of  potash   ...      60  grs. 

Distilled  water    i£  ozs. 

Ninety  minims  each  of  A  and  B  are  mixed  and  spread  over  a 
well-sized  sheet  of  paper  26  X  20  ins.  Potassium  chlorate  may 
be  added  to  increase  contrast.  Expose  under  a  negative  until 
the  faintest  trace  of  an  image  is  visible ;  then  develop  upon  a 
cold  solution  made  as  follows  : — Make  a  saturated  solution  of 
neutral  oxalate  of  potash  in  cold  distilled  water,  and  dissolve  dry 
ferrous  oxalate  in  this  to  saturation.  Wash  in  water  acidified 
with  hydrochloric  acid  about  \\  per  cent,  till  the  drawings  are 
colourless.    Wash  thoroughly  and  dry. 

Formula  for  Mercuro-Ura?wlype. 
Solution  A. 
Saturated  solution  of  uranium  chloride. 


Solution  B. 
Saturated  solution  of  mercuric  chloride. 
347 


Pla] 


DICTIONARY  OF  PHOTOGRAPHY. 


Sensitising  Liquid. 

Solution  A   i  oz. 

B   i  drm. 

About  170  minims  will  be  required  to  sensitise  a  sheet  26  X 
20  ins.  Expose  behind  a  negative  until  the  image  attains  full 
strength,  and  then  float  on  a  dilute  solution  of  chloride  of  gold 
or  chloro-platinite  of  potash  to  tone  it.  Then  wash  in  water 
acidified  with  hydrochloric  acid  and  wash ;  or  the  toning  may- 
be omitted,  and  the  print  merely  washed  in  acidified  water,  and 
then  thoroughly  washed  and  dried. 

Palladiotyfie. 

No  distinct  formulae  are  given,  but  the  operations  are  thus 
described  : — 

"  1st.  Coating  the  paper.  This  may  be  done  with  either 
uranic  chloride,  ferric  oxalate,  or  sodic  ferric  oxalate,  or  a 
mixture  of  any  or  all  of  these. 

"  2nd.  Exposure. 

"3rd.  Development.  Half  a  drachm  of  a  15-grain  solution  of 
sodio-chloride  of  palladium  is  diluted  with  about  1  oz.  of  water, 
and  the  print  floated  thereon  face  downwards.  It  is  better  to 
add  a  trace  of  hydrochloric  acid  to  the  developer. 

"4th.  Fixing  as  in  platinotype. 

The  result  will  be  a  print  like  a  platinum  print,  only  of  a  nice 
warm  tone,  which  may  be  rendered  colder  by  adding  a  trace  of 
platinum  to  the  developer. 

Platinum  (Ger.,  P latin ;  Fr.,  Platine ;  Ital.,  P latino). 
Pt  =  1967.  Synonym  :  Platina.  This  metal  occurs  usually  in 
the  free  state,  the  chief  source  of  supply  being  Mexico,  Brazil, 
and  Siberia.  It  is  a  silvery  white  metal,  having  specific  gravity 
21*5.  When  in  an  extremely  fine  state  of  division,  it  is  absolutely 
black,  and  is  one  of  the  most  permanent  and  immutable  of  all 
metals.  It  is  tolerably  hard,  very  difficult  of  fusion,  not  dissolved 
by  hydrochloric,  nitric,  or  sulphuric  acid,  and  only  slightly  acted 
upon  by  some  alkaline  substances. 

Platinum  Perchloride  (Ger.,  Platinwasserstoffchlorid ; 
Fr.,  Bichlorure  di  platine;  Ital.,  Bicloruro  di  platind). 
PtCl42HCl,6H20  =  489.     Synonyms  :   Bichloride  of  Platinum, 

348 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pla 


Platinum  Chloride,  Platinic  Chloride,  Muriate  of  Platina,  Chloro- 
platinic  Acid.  This  salt  is  prepared  by  dissolving  metallic 
platinum  in  aqua  regia.  It  occurs  in  small  brownish-red  masses 
extremely  deliquescent,  forming  a  deep  orange  or  brownish- 
orange  solution.  Very  soluble  in  alcohol  and  water.  It  is  used 
for  preparing  chloroplatinite  of  potash,  and  has  been  suggested 
for  toning  prints  and  collodion  positives.  This  salt  readily 
combines  with  the  chlorides  of  potassium,  sodium,  and  ammonium 
to  form  double  salts — e.g.,  PtCl42KCl. 

Platinum  Toiling.  Either  with  the  desire  for  greater 
variation  in  the  tones,  or  for  possible  greater  permanence  of  the 
image,  platinum  has  been  applied  to  the  toning  of  silver  images, 
and  whilst  rich  brown  blacks  and  cool  sepias  are  obtained  it 
does  not  seem  possible  to  obtain  pure  blacks  as  when  using 
platinotype  paper.  There  are  several  conditions  which  are 
essential  for  successful  work.  The  prints,  whether  on  gelatino- 
chloride,  plain  salted,  or  smooth  or  rough  surface  paper,  need 
not  be  printed  any  deeper  than  usual.  The  platinum  salt 
employed  must  be  the  chloro-platinite,  the  ordinary  perchloride 
being  comparatively  useless  for  this  purpose.  The  print  must 
be  absolutely  freed  from  soluble  silver  salts  before  toning,  the 
toning  bath  must  be  acid,  and  the  paper  must  be  free  from 
all  acid  and  soluble  platinum  salts  before  fixing,  or  else  the 
whites  become  yellowed.  To  free  the  print  from  silver  nitrate 
the  best  thing  to  do  is  to  allow  it  to  soak  for  five  minutes  in  a 
solution  of  salt  and  water  2  ozs.  to  the  pint,  and  then  wash  so 
as  to  free  it  from  excess  of  salt,  and  then  place  in  the  toning- 
bath.  Numerous  formulae  have  been  suggested  for  this,  but 
the  most  suitable  are  either  that  of  Stieglitz,  which  is — 

A.  Oxalate  of  potash    ...       ...    256  grs. 

Acid  phosphate  of  potash  ...       ...       ...    128  ,, 

Distilled  water       ...       ....       ...       ...       5  ozs. 

B.  Chloroplatinite  of  potash   ...       ...       ...     60  grs. 

Distilled  water       ...    2  ozs. 

For  use  take  of 

Solution  A   3  parts. 

Solution  B   ...    1  ,, 

Distilled  water    2  ,, 

349 


irnej  dictionary  of  photography. 

This  can  be  brushed  over  the  well-washed  print.  A  far 
simpler  bath  is  obtained  by  using  the  chloro-platinite  with  an 
acid  or  acid  salt,  and  provided  nitric  or  hydrochloric  acid  is 
not  used  there  is  not  much  difference  to  be  detected.  If  a 
faintly  acid  and  somewhat  weak  bath  be  used,  such  as  is 
obtained  by  using  a  saturated  solution  of  cream  of  tartar,  warm 
sepia  tones  are  obtained,  whereas,  by  using  stronger  acids,  such 
as  phosphoric  or  citric  and  a  greater  concentration  of  bath, 
deeper  tones  are  obtained. 

No.  i  for  Sepia  Tones. 

Acid  tartrate  of  potash  (cream  of  tartar)     ...  60  grs. 

Potassium  chloroplatinite    1  ,, 

Distilled  water  ...       ...    6  ozs. 

No.  2  for  Blacker  Tones. 

Citric  acid         ...       ...       ...       ...       ...  60  grs. 

Potassium  chloroplatinite       ...       ...       ...       2  ,, 

Distilled  water   2  ozs. 

Not  much  guide  as  to  the  final  tone  of  the  print  is  to  be  obtained 
by  examining  them  by  transmitted  light.  After  toning  the  prints 
should  be  well  washed,  and  then  passed  into  solution  of  carbonate 
of  soda,  about  1  oz.  to  the  pint,  and  thence  into  the  fixing 
bath. 

Pneumatic  Holder.  A  convenient  little  apparatus  for  holding 
plates  for  the  purpose  of  coating  them,  used  chiefly  in  the  old 
collodion  days,  the  principle  relying  upon  the  pressure  of  the 
atmosphere  to  keep  the  plate  in  its  position  on  the  holder,  due 
to  the  india-rubber  ball  being  partially  exhausted  of  air. 

Poisons.  Some  of  the  chemicals  used  in  photographic  pro- 
cesses are  poisonous  when  taken  internally  or  when  absorbed 
through  the  skin.  The  table  on  p.  351  will  be  of  some  assistance 
on  that  point.  Fluoric  acid  when  applied  to  the  skin,  even  in 
a  dilute  state,  causes  painful  ulcers,  and  1  in  80  can  also 
cause  irritation  and  tenderness.  Bichromate  of  potash  and 
cyanide  of  potash,  when  applied  to  cuts,  wounds,  and  abrasions, 
are  absorbed,  and  cause,  the  first  painful  sores,  the  latter 
death. 

3SO 


DICTIONARY  OF  PHOTOGRAPHY. 


[Poi 


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CU  73 


DICTIONARY  OF  PHOTOGRAPHY. 


Porcelain  Pictures.   See  Enamels  and  Opalotypes. 
Portrait  Lens.   See  Lens. 

Portraiture.  The  portrayal  of  the  features  of  those  with 
whom  they  are  in  daily  contact  may  be  said  to  be  the  summit  of 
ambition  of  many  amateurs,  and,  as  a  rule,  it  is  their  weakest 
point,  and  naturally  the  stronghold  of  the  professional.  So 
many  happy  possessors  of  a  camera  consider  that  all  they  have 
to  do  is  to  stick  their  sitter  down  somewhere  near  a  strong 
light,  tell  this  much-to-be-pitied  individual,  after  he  or  she  has 
become  thoroughly  worn  out  and  tired  of  the  whole  thing  from 
frequent  changes  of  position  and  camera,  this  being  wrong,  and 
then  something  else  requiring  readjustment,  to  look  pleasant — 
fancy  looking  pleasant  when  you  wish  the  whole  thing  elsewhere  ! 
— and  then,  after  the  usual  operations,  a  first-class  pleasing 
memento  is  expected  to  be  the  result.  They  expect  in  a  few 
trials  to  reach  the  same  standard  that  it  has  taken  the  professional 
years  of  apprenticeship,  hard  work,  and  study  to  learn  ;  and 
should  their  results  be  any  but  first-class  and  pleasing,  the 
blame  is  thrown  on  the  lens,  camera,  light,  sitter,  the  bad 
plates,  anywhere  but  on  the  right  shoulders.  Portraiture  needs 
a  keen  appreciation  of  the  value  of  light  and  shade,  a  good 
knowledge  of  what  the  lens  will  do,  and  considerable  artistic 
skill  and  ability.  It  is  impossible  to  give  complete  directions  for 
the  successful  working  of  this  branch  of  photography,  but  some 
hints  may  possibly  be  gained  from  the  following  notes.  One  of 
the  most  important  of  all  accessories  for  home  portraiture  is  the 
background.  Nothing  is  so  painful  as  to  see  a  fine  head  spoilt 
by  some  not  always  artistic  wall  paper,  which  is  generally  so 
sharply  focussed  that  one  may  count  every  petal  on  some  impos- 
sible flower,  or  see  joins  and  irregularities  in  the  said  paper.  If 
we  want  to  turn  out  artistic  work,  wall  papers  must  be  avoided 
as  a  rule  ;  rarely  do  the  patterns  lend  themselves  for  use  as  back- 
grounds, and  even  when  they  do  they  should  be  thrown  out  of 
focus,  so  as  to  become  mere  suggestions  rather  than  concrete 
shapes.  There  are  of  course  portable  backgrounds  to  be  obtained 
commercially,  of  perfect  quality,  and  at  such  a  price  as  to  bring 
them  within  the  reach  of  all.  But  many  of  us  have  a  great 
hankering  after  home-made  contrivances,  and  the  few  hints  we 
may  give  may  be  of  service  to  those  handy  with  carpenter's 

352 


DICTIONARY  OF  PHOTOGRAPHY.  [Por 

tuolt  The  first  background  we  ever  used  was  the  so-called  felt 
paper  or  wide  brown  paper,  as  used  under  carpets  ;  this  may  be 
obtained  from  almost  any  house  furnishers,  about  six  feet  wide 
and  any  length.  Having  obtained  the  paper,  the  next  question 
is  how  to  mount  it.  For  this  purpose  procure  an  ordinary  blind 
roller  of  the  requisite  length,  and  fold  down  six  inches  of  the 
paper  at  one  end,  and,  having  some  thin  glue  read)',  coat  the 
turned  down  portion  of  the  paper  with  the  glue,  place  the 
roller  under  the  fold,  and  dab  quickly  into  contact  with  a  cloth. 
It  is  obvious  that  we  mean  the  underneath  side  of  the  turned 
down  strip  is  to  be  glued,  the  turning  down  being  merely  a 
device  to  obtain  the  paper  straight  on  the  roller,  otherwise  we 
may  get  some  nasty  bulges  in  the  background.  When  the 
glue  is  dry,  a  sufficient  length  of  the  paper  may  be  cut  off, 
and  a  lath  glued  into  it  in  the  same  way  as  the  roller.  About 
eight  feet  will  be  found  a  convenient  length,  and  we  have  thus  a 
background  six  feet  by  eight  feet  of  one  uniform  tint.  This  will 
serve  its  purpose  well,  and  may  be  rolled  up  and  stowed  away  in 
some  convenient  corner  when  done  with.  A  more  durable  back- 
ground may  be  made  of  the  materials  used  for  blinds,  and  with 
this  we  can  obtain  two  or  three  backgrounds  without  much 
expense.  Thus  we  may  choose  a  pale  buff,  which  will  give  us 
a  pale  tint  suitable  for  dark  people  ;  and  by  choosing  also  a  deep 
green  or  deep  red,  we  can  obtain  a  dark  background  for  fair  hair, 
white  or  light  dresses,  and  children.  There  are  one  or  two 
points  in  connection  with  the  background  which  it  will  be  as  w  i  ll 
to  mention  before  proceeding  any  farther.  The  first  is,  when 
mounting  cloth  backgrounds,  it  is  advisable  to  nail  them  to  the 
roller,  exactly  like  a  blind,  and  an  important  point  in  this,  as  in 
the  paper  backgrounds,  is  to  get  them  to  hang  straight  ;  this  can 
best  be  done  by  commencing  to  nail  in  the  centre,  working  out 
to  the  edges,  and  giving  the  cloth  at  each  nail  a  gentle  stretch  ; 
we  then  get  no  bulges  or  wrinkles.  The  second  point  refers  to 
the  choice  of  colour.  It  is  well  known  that  the  illumination  in 
most  rooms  is  poor,  and  it  is  also  a  well-recognised  fact  "  that 
coloured  substances  undergo  changes  of  tint  when  they  are  seen 
under  a  very  bright  or  very  feeble  illumination  "  :  hence  it  is 
advisable  to  choose  rather  a  lighter  tint  of  any  colour  than  we 
actually  desire,  as  in  the  poorly  lit  room  the  tint  will  actually 
appear  darker  than  it  really  is.    The  next  question  to  consider  is 

353  a  a 


Por]  DICTIONARY  OF  PHOTOGRAPHY. 

how  to  support  the  background,  and  this  requires  practically  a 
frame  or  stand,  which  can  easily  be  made  from  deal  by  a  car- 
penter, or  even  by  the  amateur  himself.  The  frame  should  take 
the  form  of  an  inverted  V,  thus  a,  and  one  of  these  at  each  end 
will  be  quite  sufficient  to  support  any  background  it  may  be 
desirable  to  use.  Personally  we  use  two  iron  rods,  which  were 
originally  used  as  curtain  suspenders,  we  fancy  ;  these  are  bound 
together  near  one  end,  so  as  to  leave  two  little  cross-pieces  about 
six  inches  in  length,  which,  crossing  over,  form  a  fork,  in  which 
the  ends  of  the  roller  rest ;  these  at  each  end  serve  to  support 
the  background.  The  lower  ends  of  the  iron  rods  are  inserted 
in  holes  bored  in  pieces  of  deal  six  inches  square  and  two  inches 
thick  ;  this  prevents  the  rods  slipping,  and  enables  one  to  shift 
the  background  about  as  one  likes.  In  attempting  portraiture  in 
rooms  not  specially  built  for  that  purpose  the  great  difficulty  to 
contend  with  is  want  of  light,  and  power  to  control  what  light 
there  is.  The  light  streaming  in  from  a  narrow  window  which 
has  not  always  an  uninterrupted  view  of  the  sky  gives  a  some- 
what bright  illumination  to  one  side  of  a  sitter's  face,  and  the 
other  is  in  somewhat  dark  shadow,  and  as  the  shadow  side  of  the 
face  is  illuminated  by  light  reflected  from  surrounding  objects, 
such  as  dark-coloured  furniture,  or  frequently  somewhat  yellowish 
paper,  etc.,  the  sensitive  salt  of  silver  in  our  dry  plate  has  a  ten- 
dency to  exaggerate  this  shadow,  and  without  an  inordinately 
long  exposure  we  get  "  soot  and  whitewash"  results,  or,  in  other 
words,  one  side  of  the  face  bare  glass  without  any  detail,  and  the 
other  side  very  dense ;  so  that  to  obtain  the  detail  in  the  latter  in 
the  print  we  over-expose  the  former,  and  the  print  is  too  harsh. 
To  modify  this  state  of  things  must  be  our  great  endeavour,  and 
we  shall  see  how  to  do  this  in  lighting,  or  rather  placing  of  sitter, 
and  also  by  the  use  of  reflectors.  Now  reflectors  may  be  of  two 
kinds,  which  we  may  call  the  small  and  intense,  such  as  a  mirror, 
and  the  large  and  diffused,  like  a  sheet.  The  latter  will  be 
found  of  far  greater  service  that  the  former,  and  to  be  of  service 
must  be  of  large  size  and  properly  placed — of  sufficiently  large 
size  to  be  placed  not  only  on  some  support,  but  also  to  be  spread 
out  on  the  floor.  A  convenient  support  for  this  reflector  is  the 
domestic  clothes-horse.  We  may  as  well  digress  here  a  moment 
and  give  one  hint  to  all  would-be  home  portraitists,  and  that  is 
irake  friends  with  the  ruling  spirit  of  the  house,  whether  wife, 

354 


DICTIONARY  OF  PHOTOGRAPHY.  [Por 

mother,  or  sister,  as  to  turn  out  decent  work  means  some  upset- 
ting of  the  room  and  utilisation  of  household  property  ;  so  first 
of  all  get  on  the  right  side  of  the  powers  that  be,  and  secondly 
always  clear  up  after  you — put  things  back,  as  far  as  lies  in  your 
power,  in  the  position  you  found  them.  Ladies  will  always  look 
with  disfavour  on  any  one  who  turns  the  place  upside  down,  and 
even  when  "  you  men  "  put  curtains,  chairs,  etc.,  to  rights,  the 
gentle  hand  must  give  the  final  arranging  artistic  touch.  Curtains 
are  sufe  to  drape  the  window,  so  these  must  be  pulled  right 
back,  and  pinned  or  held  back  by  a  chair,  etc. ;  blinds,  Venetian 
or  otherwise,  must  be  pulled  right  up  ;  and  finally  windows  must 
be  clean — a  dirty  window  will  stop  out  50  per  cent,  of  the  light 
sometimes.  If  the  windows  are  of  the  French  fashion — that  is, 
opening  out  or  in  like  a  door — open  them  wide,  if  not  too  cold. 
Finally,  when  necessary,  use  a  reflector  outside  the  window  ;  we 
all  know  how  snow  on  the  ground  lights  up  the  room,  so  use  a 
reflector,  and  use  a  big  one.  We  daren't  suggest  putting  a  sheet 
out,  because  this  might  get  us  into  serious  trouble  with  the  ladies, 
but  "  we  are  free  to  confess  "  that  we  do  it,  though  under  protest 
from  somebody.  When  it  comes  to  full  length,  we  get  another 
question  to  consider,  that  of  suitable  accessories,  and  when  con- 
sidering the  subject  of  posing,  we  shall  note  a  point  or  two  which 
may  be  useful,  as  very  fine  results  may  be  obtained  from  taking 
a  portrait  ot  anybody  engaged  at  work,  or  seated  by  the  fire,  or 
reading,  writing,  etc.,  and  in  such  cases  the  picture  would  be  in- 
complete without  the  actual  and  necessary  furniture  in  the  room, 
and  in  this  case,  too,  we  may  admit  the  otherwise  inadmissible 
wall  paper.  Without  going  to  any  outlay,  a  capital  backgrouud, 
especially  for  children,  is  the  screen  to  be  found  in  so  many 
houses,  and  the  same  may  also  serve  for  the  support  of  a  ready- 
made  background  which  may  be  found  in  every  house — namely, 
a  blanket ;  or  the  screen  may  be  used  to  support  the  reflector. 
One  of  the  greatest  faults  in  amateur  portraiture  is  the  use  of  the 
doublet  or  rapid  rectilinear  lens.  This  is  a  statement  that  will 
surprise  many  who  read  it ;  still,  it  is,  we  think,  none  the  less 
true.  The  rectilinear  lens  has  such  a  depth  of  focus  and  cuts  so 
sharply  that  we  lose  that  softness  and  roundness  which  is  ob- 
tained by  the  use  of  the  portrait  lens,  and  it  is  difficult  to  com- 
pensate for  this  by  any  system  of  throwing  the  image  out  of 
focus  ;  and  the  rectilinear  lens  has  such  an  enormous  width  of 

355 


Por]  DICTIONARY  OF  PHOTOGRAPHY. 

angle  that  we  have  to  get  so  near  the  object  to  obtain  an  image 
of  any  size,  that  we  have  consequently  an  increase  of  focal  length 
and  diminution  of  ratio  aperture,  which  makes  our  lens  abnor- 
mally slow.  We  may  use  either  a  portraits  lens  or,  as  these 
when  of  good  quality  run  into  a  heap  of  money,  we  may  get  the 
next  best  lens  for  portraiture,  and  that  is  the  single  lens  of  fairly 
long  focus,  working  at  rather  a  larger  aperture  than  usual — viz., 
y/8.  There  is  sufficient  spherical  aberration  present  with  such 
an  aperture,  as  a  rule,  as  to  have  no  baneful  influence  and  yet 
give  us  roundness  and  softness.  Personally,  we  have  rigged  up 
a  compromise,  and  that  is  as  follows.  We  managed  to  get  hold 
of  some  unmounted  single  or  meniscus  landscape  lenses,  and  we 
use  these  in  a  mount  specially  made  for  us,  and  we  are  thus  able 
by  a  little  calculation  to  obtain  any  focal  length  and  any  ratio 
aperture  we  want.  The  lenses  are  of  22,  18,  16,  13,  10,  and  8  in. 
focus  respectively.  We  had  a  tube  of  brass  made  with  a  cell  to 
fit  in  each  end  ;  into  these  cells  we  can  slip  any  one  of  the  above 
lenses,  and  a  ring  of  brass  keeps  the  lens  in  its  place.  The  tube 
is  7.\  ins.  long,  and  the  cells  screw  in  till  there  is  only  two  inches 
between  the  inner  surfaces  of  the  lenses.  The  diaphragm  slot 
is  just  midway.  Now,  according  to  the  well-known  rule,  multiply 
the  foci  of  the  two  combinations  together,  and  divide  by  the  sum 
obtained  by  adding  them  together  and  subtracting  the  distance 
of  separation,  it  is  quite  possible  to  reckon  out  any  focus  we  like. 
Let  us  take,  for  instance,  the  22  and  18-in.  lenses — 22  x  18-r- 
[(22  +  18)  —  2]=396-r38=io^  focal  length.  Now,  the  full  aper- 
ture of  our  lens  is  if  ;  therefore  we  get  a  focal  length  of  10^  ins. 
and  a  ratio  aperture  off/6'$,  at  which  there  is  sufficient  outstand- 
ing spherical  aberration  to  give  us  softness.  Or  we  may  use  the 
18  and  16-in.  lenses,  and  then  we  get  18  x  1*6  [(18  +  16)  — 2] 
=  288  -r-  32  =  9,  and  the  aperture  will  then  be  //4'8,  and  we 
must,  or  may,  stop  down  with  advantage  ;  or,  if  we  take  the  two 
extremes,  we  get  22  X  8  -r  [(22  +  8)  —  2]  =  176  —  28  =  6*3,  and 
we  get  an  aperture  f/S'g,  which  requires  a  good  deal  of  stopping 
down.  This  arrangement  is  not  optically  and  scientifically  per- 
fect, but,  at  any  rate,  it  will  just  do  what  we  want  it  to,  and  we 
have  a  very  convenient  and  efficient  combination  lens  with  which 
we  can  obtain  any  focal  length,  and  consequently  any  sized 
image,  so  that  we  can  actually  work  our  lens  at  any  aperture  we 
like  without  having  to  get  too  near  the  sitter,  and  thus  decrease 

356 


DICTIONARY  OF  PHOTOGRAPHY. 


[Por 


the  ratio  aperture.  The  next  point  to  consider  is  the  camera  and 
tripod.  This  may  be  the  ordinary  one  we  are  always  in  the  habit 
of  using  ;  but  if  we  want  to  avoid  any  outcry  we  had  better  shoe 
the  tripod  points  with  bits  of  cork  to  prevent  damage  to  carpets, 
etc.  A  swing-back  is  extremely  convenient  here.  No  other  point 
in  the  camera  or  its  appurtenances  requires  notice. 

The  next  important  consideration  is  the  plate.    This  is  always 
a  burning  question,  and  our  advice  is  to  use  as  sensitive  a  plate 
as  you  can  get  hold  of — isochromatic,  orthochromatic,  or  colour- 
sensitive,  in  preference,  because  there  is  less  work  for  retouching. 
Freckles  and  sallow  skins  and  yellowish  lighting  have,  therefore, 
less  influence.    We  prefer  personally  a  bromo-iodide  plate,  and 
always  give  as  long  an  exposure  as  we  possibly  can  without 
allowing  the  sitter  to  obviously  move,  and  for  this  reason  keep 
our  eye  on  the  sitter,  and  have  the  lens  cap  ready  to  clap 
on  the  instant  we  note  a  tremor.     The  developer  we  use  is 
eikonogen  with  hydroquinone,  but  at  present  we  have  only  con- 
sidered the  necessary  appliances,  and  consequently  the  develop- 
ment takes  a  later  place.    Every  amateur  who  wants  to  start 
portraiture  will  generally  place  his  sitter  as  close  as  possible 
to  the  window,  and  is  astonished  to  find  on  developing  his 
plate  that  he  has  obtained  a  wonderful  and  fearful  hybrid,  with 
one  side  of  the  face  black  and  the  other  white.     To  such  a 
novice  we  propound  the  startling  theory  that  the  farther  he 
puts  his  sitter  away  from  the  window  the  softer  and  more 
harmonious  the  lighting  and  the  better  the  results  obtained. 
If  he  does  not  believe  this,  let  him  set  to  work  to  prove  it 
optically  and  practically  on  himself,  for  which  purpose  all  that 
is  necessary  is  a  decent-sized  hand-glass  or  mirror,  a  chair, 
and  the  would-be  operator.    Now  let  him  seat  himself  in  the 
chair  close  to  the  window  and  hold  the  glass  so  that  he  can 
see  his  face  plainly,  and  yet  so  that  the  glass  shall  not  cast  the 
reflection  of  the  light  on  to  the  face,  and  he  will  find  that  one 
side  of  his  face  is  brightly  illuminated,  but  the  other  has  a  heavy 
black  nose  shadow,  and  the  one  ear  is  hardly  to  be  seen.  Now 
let  the  chair  be  moved  back  from  the  window  about  five  or  six- 
feet,  and  the  same  operation  be  gone  through,  when  it  will  be 
seen  that  there  is  less  contrast  between  the  light  and  shade,  and 
we  know  we  can  further  reduce  this  contrast  by  the  use  of 
reflectors.    More  is  to  be  learnt  by  thus  figuring  about  and 

357 


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DICTIONARY  OF  PHOTOGRAPHY. 


admiring  yourself  and  features  in  various  attitudes  and  positions 
as  regards  the  window,  than  any  amount  of  reading  how  to  do 
it ;  but  still,  for  the  instruction  of  those  who  like  everything 
illustrated,  the  following  diagram  will  be  of  some  assistance. 


R 

1 


Fig.  81. 

A  and  b  are  two  windows  ;  b  should  be  blocked  out  entirely 
by  blinds,  or  curtains,  etc.  The  softest  and  most  harmonious 
lighting  may  be  got  by  placing  the  sitter  about  s,  and  the  camera 
placed  about  c  or  h,  according  to  whether  profile  or  full  face  be 
required.  For  full  lengths  the  camera  will  have  to  be  placed 
about  e.  Now  for  a  few  general  hints  on  lighting,  etc.  Never 
put  your  sitter  at  f  in  the  above  diagram,  or  directly  opposite 
the  window  and  the  camera  in  the  window  recess.  Full- 
front  lighting  makes  any  face  look  like  a  plain,  flat  piece ; 
there  is  no  relief,  no  roundness,  no  shadow.  Another  important 
point  is  the  character  of  the  face,  and  the  way  this  can  be 
altered  by  varying  the  position  of  the  camera  and  lens.  Let  us 
take,  for  instance,  a  long,  thin,  cadaverous  face,  with  abnormally 
long  upper  lip,  and  sharply-defined  septum  of  the  nose,  with 
rather  receding  nostrils.  Now  let  us  place  the  lens  level  with 
the  nose,  and  what  do  we  see  ?  Why,  the  lip  and  nostril 
natural,  it  is  true,  but  too  long  and  too  prominent.  Placing  the 
lens  so  as  to  slightly  look  down  on  the  nose  and  lip  reduces 
these  to  pleasing  proportions,  whilst  if  we  place  the  lens  level 
with  the  breast,  so  as  to  look  up  to  the  nose  and  lip,  the 
abnormal  length  is  intensified.  We  might  go  on  multiplying 
instances  in  this  fashion,  but  must  leave  the  operator  to  find 
these  things  out  for  himself.  Some  people,  especially  those 
who  do  much  head  work  or  who  have  experienced  great  troubles 
or  worry,  have  very  marked  furrows  or  furrow  at  the  root  of  the 

358 


DICTIONARY  OF  PHOTOGRAPHY. 


[Por 


nose  between  the  eyebrows,  and  on  either  side  a  protuberance 
more  or  less  marked,  which  give  great  character  to  the  face,  and 
which  the  possessors  are  sometimes  very  proud  of.  The  face 
should  be  so  lighted  that  these,  or  at  least  one,  is  distinctly 
visible,  and  a  very  good  position  is  the  profile  just  showing  a 
little  of  the  further  eye.  Another  important  point  to  be  con- 
sidered is  the  presence  of  scars,  moles,  and  other  marks  ;  when 
these  are  present,  it  is  of  course  absolutely  necessary  to  take 
the  other  side  of  the  face,  unless,  in  the  case  of  a  fair  sitter, 
when  sometimes  a  small  mole  or  beauty  spot  is  very  effective, 
giving  piquancy  to  the  face.  All  professional  photographers  and 
all  authorities  upon  portraiture  state  that  one  side  of  the  human 
face  is  better  or  more  perfect  than  the  other.  Thus  H.  P.  Robin- 
son, the  best  known  authority,  in  his  excellent  little  book,  "  The 
Studio,  and  What  to  Do  in  It,"  p.  50,  says,  "  The  first  thing  to 
decide  when  you  see  your  sitter  should  be,  '  Which  side  of  his 
face  will  make  the  best  picture  ? '  This  consideration  seldom 
gives  an  experienced  operator  any  trouble.  To  one  who  is  in 
the  habit  of  observing,  the  sides  of  every  face  differ  so  much  and 
in  such  a  definite  manner,  that  a  glance  is  all  that  is  necessary 
to  settle  the  question  ;  but  the  young  photographer  will  want  to 
know  how  to  select  and  have  some  rule  for  the  selection.  If 
you  will  look  critically  at  a  full  face  (or  the  photograph  of  a  full 
face  would  be  better,  as  it  would  enable  you  to  measure),  you 
will  find  that  the  eyes  are  not  level — one  is  higher  than  the 
other.  This  is  almost  invariable,  and  is  one  of  the  peculiar 
instances  in  which  nature  insists  on  variety,  even  where  uniformity 
would  seem  to  be  proper.  ...  I  keep  an  illustrated  catalogue  of 
all  the  portraits  I  take,  and  on  looking  through  several  volumes 
...  I  found  that  about  four  out  of  five  of  the  portraits  were 
taken  looking  to  the  right,  showing  that  I  had  in  these  instances 
chosen  the  left  side  as  the  best."  An  important  point,  and  one 
often  neglected  by  the  amateur  operator,  is  the  direction  of  the 
eyes.  It  is  no  uncommon  thing  to  see  a  rather  fine  large  head, 
with  good  gradation  and  modelling,  facing  a  point  slightly  to  one 
side  of  the  camera,  probably  about  six  inches  from  the  lens, 
whereas  the  eyes  are  directed  to  a  point  at  least  three  times  that 
distance  from  the  camera.  In  other  cases  the  eyes  are  elevated 
till  it  might  be  assumed  that  the  sitter  was  trying  to  illustrate 
the  forcible  but  not  over-elegant  phrase,  "a  dying  duck  in  a 

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DICTIONARY  OF  PHOTOGRAPHY. 


thunderstorm.''  The  question  of  how  to  avoid  the  "  dying  duck  " 
expression  and  how  to  obtain  a  pleasing  expression  on  the 
sitter's  face  is  one  by  no  means  easy  to  decide,  the  latter  portion, 
at  any  rate.  A  very  good  plan  is  to  place  a  decent-sized  mirror 
in  front  of  the  sitters,  and  allow  them  to  look  at  themselves  in 
that,  when,  as  a  rule  with  sitters  of  mature  age  and  sound 
judgment,  it  is  by  no  means  a  difficult  operation  for  them  to  so 
command  the  facial  muscles  as  to  put  on  a  pleasing  look  when 
they  can  see  themselves.  The  old  formula  of  "  Wet  your  lips 
and  look  pleasant,  please"  has  almost  disappeared,  simultaneously 
with  the  habit  of  the  operator  turning  his  back  on  the  sitter. 
There  is  a  tale,  the  veracity  of  which,  however,  we  will  not 
vouch  for,  that  a  tintype  worker  used  to  draw  on  the  once  white- 
washed wall  of  his  studio,  and  tell  his  visitors  to  "  look  at  that 
and  look  pleasant,"  possibly  a  difficult  matter.  We  have  per- 
sonally, however,  worked  in  a  studio  where  it  was  customary  to 
tell  sitters  to  look  at  a  little  gaudily-painted  box,  and  at  the 
same  moment  as  the  lens  shutter  was  raised,  a  little  Jack-in-the- 
box  sprung  up  and  "  put  his  thumb  unto  his  nose  and  stretched 
his  fingers  out."  The  effect  of  this  on  the  sitters  was  marvellous; 
in  some  a  genuine  home-made  Cheshire  grin  appeared,  in  others 
the  jaw  dropped  in  surprise,  in  juveniles  the  eyes  extended ;  so 
finally  poor  Jack  was  relegated  to  the  shelf,  as  these  results  were 
by  no  means  artistic.  It  is  far  better  to  use  merely  a  looking- 
glass  ;  some  writers  use  a  picture,  others  have  recommended  a 
clock,  etc.  Whatever  is  used,  however,  let  it  be  a  fair  size,  and 
tell  your  sitter  not  to  be  afraid,  but  to  blink  his  or  her  eyes  as 
usual,  and  not  to  fix  them  in  a  steady  glare,  as  though  trying  to 
freeze  somebody.  Above  all  things,  let  your  sitters  be  natural. 
If  a  lady,  give  her  a  piece  of  needlework,  and  tell  her  to  work  at 
it,  then  drop  it  in  her  lap,  and  look  up  as  though  going  to  speak. 
For  young  ladies  a  doll,  animate  or  inanimate,  may  be  of  use  ;  in 
the  former  case,  however,  it  is  preferable  to  have  one  that  will 
sleep — some  won't,  or  at  least  we  have  come  to  that  conclusion. 
For  a  gentleman,  give  him  a  stick,  cigarette,  cigar,  or  pipe,  or  let 
him  stand  by  a  table  on  which  lie  hat,  gloves,  and  stick,  and  tell 
him  to  begin  to  pick  them  up.  For  smaller  boys,  a  top  or  game 
may  be  utilised.  Who  does  not  know  Rejlander's  picture,  "  The 
Game  of  Chess "  ?  Here  there  is  an  excellent  chance  for  a 
group  ;  two  persons  playing  chess,  one  leaning  back  looking 

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DICTIONARY  OF  PHOTOGRAPHY.  [P()r 

rather  pleased,  the  other  leaning  over  the  board  "with  bent 
brow  and  eye  intent,"  whilst  behind  a  third  may  stand  smiling 
at  the  triumphant  player.  Call  this  "  A  Poser  "  or  "  In  a  Fix," 
what  you  please,  only  whatever  you  do  carry  the  thing  out 
properly.  Place  the  chess  men  in  a  difficult  position — not  as 
we  saw  them  a  week  or  two  back  in  a  picture,  a  chess  board 
without  a  single  piece  lost ;  not  that  we  mean  to  infer  difficult 
situations  do  not  occur  then,  but  they  are  more  likely  to  at  the 
end  of  a  game.  Then  again,  for  a  group  of  four,  what  is  better 
than  a  scientific  rubber  of  whist  ?  Here,  too,  put  your  accessories 
in  ;  the  markers,  the  second  pack,  the  played  cards  in  the  middle 
of  the  table,  the  tricks  won,  etc.  We  may  possibly  make  the 
title  tell  the  tale  ;  for  instance,  "  The  call  for  trumps."  Or  again, 
let  one  party  be  scoring,  the  other  counting  the  tricks — "  Two 
by  tricks  and  honours  easy ;  "  or  a  more  difficult  subject  still, 
"  Trumped  my  ace,  by  gad,  sir  !  "  Surely  this  recalls  the  choleric, 
stout  old  gentleman,  rising  in  hot  haste,  his  hand  flung  down,  the 
chair  upset  behind  him,  whilst  the  luckless  wight  who  has  been 
unfortunate  enough  to  "  trump  my  ace,"  stares  in  shivering 
astonishment  at  his  wrathful  partner  and  triumphant  opponents, 
one  of  whom  leans  back  enjoying  the  joke  with  a  rude  guffaw, 
the  other  calmly  smiling  at  the  wretched  culprit.  We  might  go 
on  giving  our  readers  hints  without  end,  but  must  content  our- 
selves by  impressing  on  them  the  importance  of  having  every- 
thing in  harmony.  Give  your  sitters  something  to  do  or  hold 
that  they  are  in  the  habit  of  using,  and  they'll  immediately  fall 
into  natural  attitudes  ;  but  give  a  man  a  violin  or  something  he 
knows  nothing  about,  and  he  will  immediately  look  as  though  it 
was  some  strange  thing,  and  nothing  you  can  do  will  prevent  it. 
We  have  considered  briefly  the  single  figure,  and  noted  a  possible 
chance  of  a  group  indoors.  We  have  now  to  consider  some 
general  principles  to  be  observed  in  outdoor  portraiture.  There 
is  one  background  which  is  very  common  and  is  by  no  means 
artistic,  that  is  a  trellis  work,  sometimes  partially  covered  with 
ivy,  jessamine,  or  Virginia  creeper,  which  is  too  often  sufficiently 
thrown  out  of  focus  to  make  the  interstices  of  the  trellis  round, 
patchy  spots,  which  attract  the  eye  before  the  figure  or  face. 
Ivy,  Virginia  creeper,  or  any  other  plant  or  a  shrub  may  form  a 
very  pretty  artistic  background,  but  it  should  never  be  as 
sharply  focussed  as  the  sitter,  nor  sufficiently  fuzzy  to  lose  its 

361 


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outline  and  character.   Never  take  your  subject  standing  against 
a  wall,  the  top  of  which  just  comes  across  the  back  of  his  neck; 
this  gives  one  an  idea  of  the  guillotine  or  block,  which  is  not 
pleasant.    Always  look  carefully,  too,  to  see  that  there  is  no 
obtrusive  branch  or  flower  which  apparently  grows  out  of  his 
neck  or  the  top  of  his  head.    We  have  a  most  curious  example 
of  amateur  portraiture  in  which  the  sitter,  a  lady,  wears  a  hat 
trimmed  with  some  flowers,  and  from  the  position  she  is  placed 
in  it  looks  for  all  the  world  as  though  she  was  supporting  a 
whole  rose  tree  on  her  head.    A  sitter  should  never  be  placed 
in  the  sun,  nor  under  a  tree  through  the  branches  or  leaves  of 
which  the  sun  shines  on  him  in  patches,  or  the  resulting  prints 
will  give  one  the  idea  of  a  piebald  sitter.    Very  good  results 
can  frequently  be  obtained  by  placing  the  sitter  in  the  angle 
of  a  wall  facing  the  north  or  north-west ;  but  it  is  far  prefer- 
able to  use  a  lawn  studio,  such  as  sold  by  various  firms.  We 
have  used  one  made  on  the  same  principle  for  some  time  with 
the  best  results.    With  such  a  studio  one  can  command  the 
lighting,  and  obtain  results  otherwise  impossible,  and  the  cost 
is  but  small.     Outdoor  work  gives  us  very  good  chances  for 
happy  groupings,  and  we  shall  note  one  or  two  possibilities, 
leaving  our  readers  to  carry  out  more  fully  the  ideas  we  sketch. 
Tennis  parties  are  capital  opportunities,  not  only  for  flirting,  but 
also  for  group  work.    Thus  we  may  have  two  gentlemen,  one  in 
the  act  of  tossing,  the  other  watching  him  ;  and  two  young 
ladies  standing  together  having  a  confidential  chat,  and  "  Tossing 
for  Partners  "  will  tell  the  story.    In  the  background  we  can 
place  a  group  of  onlookers,  and   perhaps  a   couple  quietly 
walking  down  a  path  or  across  the  grass  for  a  quiet  tete-a-tete. 
Afternoon  tea  out  of  doors,  again,  affords  us  another  capital 
subject — the  tea-table,  the  presiding  divinity  and  her  attendant 
satellite,  then  two  or  three  pairs  scattered  about,  but  near.  Here 
one  must  apply  to  a  great  extent  the  well-known  rules  of  com- 
position, which  are  easily  mastered.    Whatever  you  do,  carry 
out  the  idea  well.    Do  not  crowd  everybody  together ;  give  some 
tea-cups,  others  plates,  etc.,  and  fill  cups  and  plates ;  and  don't 
let  all  your  sitters  look  straight  at  the  camera ;  let  them  chat  to 
one  another.    Again,  in  outdoor  work  there  are  plenty  of  chances 
of  making  a  pretty  picture  with  children,  either  singly  or  in 
groups  at  play,  or  at  the  swing,  etc.,  and  far  greater  success  can 

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DICTIONARY  OF  PHOTOGRAPHY. 


[Por 


be  usually  obtained,  as  the  light  is  more  even  and  stronger,  and 
therefore  a  somewhat  slow  shutter  may  be  used.  The  fortunate 
possessor  of  a  flight  of  stone  steps  leading  from  the  house  to  a 
drive  has  a  capital  chance  of  artistic  composition,  especially  if 
riding  hacks  can  also  be  had  to  order.  Thus  we  may  plant  a 
gentleman  half-way  up  the  steps,  looking  into  the  hall  of  the 
house  through  the  open  door,  or  impatiently  at  his  watch,  and 
make  a  groom  lead  a  pair  of  hacks  up  and  down  ;  and  a  title 
such  as  "Impatient"  or  "How  much  Longer  am  I  to  Wait?" 
tells  the  tale.  A  very  pretty  little  study  can  be  made  from  a 
cavalier  arranging  the  riding  habit  of  some  fair  dame,  whilst  a 
groom  holds  the  horse.  Then,  again,  we  have  the  forlorn  maiden 
watching  her  lover  riding  way,  or  anxiously  looking  for  him. 
There  are  hundreds  of  such  subjects  to  be  found,  with  a  little 
care  in  posing  so  as  to  conceal  the  art,  and  probably  one  or  two 
failures  may  be  met  with  ere  success  and  a  picture  crowns  the 
efforts.  To  the  fortunate  visitor  to  farmland  there  are  subjects 
innumerable  ready  to  hand  ;  they  only  want  seeing,  that  is  all  ; 
such  subjects  as  feeding  calves,  poultry,  etc.  Then  again  many 
a  homely  yokel  with  his  work-a-day  smock  will  make  an  excellent 
subject,  but  too  often  the  operators  seem  blinded  by  familiarity 
or  false  pride,  never  thinking  that  in  such  homely  and  true-to- 
nature  pictures  there  is  "  the  one  touch  of  nature  "  that  "  makes  the 
whole  world  kin." 

Artificial  light  for  portrait  work  may  be  classed  into  several 
divisions,  such  as  electric  light,  magnesium  ribbon,  magnesium 
flash,  oil  lamps,  and  gas.  Electric  light  we  may  dismiss  at 
once,  as  few  amongst  us  have  an  installation  ready  to  hand. 
Magnesium  ribbon  requires  more  attention,  though  this  has  to 
a  great  extent  been  replaced  by  the  flash-light.  We  need  not 
again  enter  into  the  question  of  posing,  but  merely  give  a  few 
hints  as  to  lighting.  Our  plan  is  to  pose  and  focus  the  sitter,  and 
place  on  one  side  of  the  sitter,  which  should  be  the  shadow  side, 
a  lamp  about  one  yard  off  and  slightly  to  the  front,  just  so  as  not 
to  show  on  the  focussing  screen.  We  then  use  a  pair  of  house- 
hold steps,  mount  these,  and  have  some  helper  to  remove  the 
cap  of  the  lens  at  the  moment  we  light  twelve  inches  of  magnesium 
ribbon,  which  is  waved  about.  The  steps  are  placed  slightly  to 
one  side  of  the  camera  ;  the  burning  ribbon  is  moved  about  so 
as  to  equalise  the  illumination,  and  the  two  final  inches  are 

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Por]  DICTIONARY  OF  PHOTOGRAPHY. 

brought  so  as  to  illuminate  the  shadow  side  of  face.     The  dis- 
advantage of  burning  magnesium  in  the  room  is  that  the  oxide 
or  magnesia  forrrfed  flies  about  and  settles  on  everything,  and  if 
two  or  three  exposures  have  to  be  made  one  after  the  other,  the 
negatives  obtained  subsequent  to  the  first  are  foggy  and  hazy. 
A  large  white  reflector  should  be  used  with  magnesium,  the  same, 
as  with  ordinary  daylight.    There  is  one  point  which  it  is  advis- 
able to  note,  and  that  is  that  magnesium  ribbon,  and  not  wire, 
should  be  used,  and,  secondly,  that  magnesium  ribbon  which  has 
been  kept  for  some  time  is  frequently  oxidised  on  the  surface. 
This  should  always  be  removed  by  drawing  the  ribbon  once  or 
twice  through  emery  paper,  or  else  between  the  nails.     If  much 
oxidised,  the  ribbon  will  splutter,  and  we  have  known  it  to  be 
quite  extinguished.     Few  of  our  readers  will  believe  in  the  use 
of  an  oil  lamp,  but  there  is  one  method  which  has  given  us  fairly 
good  results  for  profile  and  three-quarter-face  portraits,  and  which 
may  also  be  used  for  full  face  with  a  little  ingenuity  and  contriv- 
ance.   Still,  this  is  only  to  be  done  by  the  possessors  of  an 
optical  (or  magic)  lantern.    The  lamp  is  lighted  and  the  circle  of 
light  directed  on  to  the  sitter,  and  so  adjusted  that  no  heavy 
black  shadow  appears  on  one  side  of  the  face,  and  also  so  that 
no  black  shadow  appears  on  the  background.     An  ordinary 
lamp  should  be  used  to  light  up  the  shadow  side  of  the  face,  and 
in  all  artificial-light  work  the  room  should  be  as  well  lit  up  as 
possible,  so  as  to  avoid  great  staring  pupils  to  the  eyes ;  and  when 
this  is  not  feasible  without  giving  false  lighting,  the  sitter  should 
be  made  to  look  at  a  lighted  lamp.    The  exposure  required  with 
such  an  arrangement  is  about  twenty  to  thirty  seconds,  but  if  the 
limelight  is  to  be  had,  ten  seconds  will  be  plenty.    An  important 
point  when  working  with  artificial  light  is  to  use  as  rapid  a  plate 
as  possible,  and  it  must  be  colour- sensitive,  or  isochromatic  or 
orthochromatic.     To  the  more  ambitious  spirit  home  portraiture 
opens  up  an  enormously  wide  field  for  practical  experiments, 
which,  if  successful,  lead  to  fine  pictorial  results.    We  shall, 
therefore,  give  a  few  hints  which  may  suggest  some  subjects  to 
the  more  advanced  worker  who  is  not  afraid  of  combination 
printing,  and  the  little  trouble  it  entails.    We  shall  take,  first  of 
all,  a  comparatively  easy  subject.     This  is  a  sitter  seated  by  a 
window  writing  or  reading  ;  through  the  window  is  seen  a  fine 
landscape.    Now,  if  we  give  sufficiently  long  exposure  for  the 

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DICTIONARY  OF  PHOTOGRAPHY.  [POT 

figure  to  obtain  detail  in  the  deeper  shadows,  we  shall  enormously 
over-expose  for  the  landscape,  so  much  so  as  to  make  it  ex- 
tremely difficult  to  develop  the  plate  so  as  to  obtain  detail  in  the 
landscape.  The  best  plan  to  obtain  such  an  effect  is  to  make 
two  exposures ;  thus  we  may  suggest  fifteen  to  twenty  seconds 
exposure  for  the  figure,  the  lighting  of  which  will  be  the  so-called 
Rembrandt  style,  whereas  probably  one  to  two  seconds  would 
be  sufficient  for  the  landscape.  We  should  give  the  longer  ex- 
posure to  the  figure  first,  and  then,  without  changing  the  position 
of  camera,  or  allowing  the  sitter  to  move,  we  should  insert  another 
dark-slide,  and  give  a  short  exposure  for  the  landscape.  On 
development  we  shall  obtain  two  negatives,  one  well  exposed  for 
the  portrait  and  over-exposed  for  the  landscape,  the  other  correctly 
exposed  for  the  landscape  and  a  mere  ghost  of  a  figure.  By 
double  or  combination  printing  we  can  obtain  a  very  good  picture. 
Another  subject  which  would  give  the  best  results  by  flash-light 
would  be  a  group  round  a  fire,  which  may  be  treated  in  the  same 
way,  and  if  a  good  negative  of  the  fire  itself  is  required,  it  is 
advisable  to  throw  salt  or  powdered  sulphur  on  to  it  to  make  a 
rather  more  actinic  blaze.  Another  class  of  subject  which  is  by 
no  means  difficult,  though  one  which  perhaps  ought  not  to  be 
included  in  picture-making,  is  the  production  of  ghost  pictures, 
which  are  by  no  means  difficult  to  make.  The  usual  method  of 
making  the  ghost  wear  white  cerecloths  is  entirely  unnecessary. 
Thus  a  subject  for  a  picture  might  very  well  be  made  by  those 
possessed  of  the  requisite  accessories — an  old  hall,  some  antique 
clothes,  etc.  We  will  call  our  picture  "  The  Ancestral  Ghost  "  ; 
the  scene,  a  long  passage  or  corridor  dimly  lighted,  preferably 
by  a  grated  window  high  up  ;  a  friend,  either  lady  or  gentleman, 
dressed  in  habiliments  of  the  last  century.  Now,  if  we  have  such 
a  corridor,  we  can  easily  make  the  picture.  A  magic  lantern 
placed  outside  the  window,  which  may  be  real  or  temporary,  may 
be  used  to  project  a  beam  of  light  on  to  the  floor,  in  the  path  of 
which  the  lady  or  gentleman  should  stand  for  about  one  or  two 
seconds  ;  the  cap  should  be  placed  oh  the  lens,  and  then  the 
subject  allowed  to  walk  away,  and  a  fairly  long  exposure  given 
to  the  corridor.  If  this  plate  be  successfully  exposed  and 
developed  we  shall  have  a  somewhat  thin  negative  of  the  corridor 
or  room,  with  a  ghostlike  figure  in  the  beam  of  light,  and  by 
printing  deeply  on  ordinary  albumenised  paper,  tinted  blue  or 

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DICTIONARY  OF  PHOTOGRAPHY. 


green,  we  shall  have  a  very  fair  picture  of  a  moonlight  visitor  in 
the  shape  of  "the  ancestral  ghost."  The  main  point  for  which 
all  our  notes  have  been  contending,  and  which  we  must  not  lose 
sight  of  in  development,  is  reduction  of  contrast  and  the  pro- 
duction of  soft,  harmonious  negatives.  The  developer,  therefore, 
should  be  chosen  with  this  end  in  view,  and  either  a  pyro 
developer  with  a  small  proportion  ot  pyro  used,  or  else  amidol 
or  metol,  directions  for  the  use  of  which  will  be  found  under  the 
various  headings. 

We  have  now  reached  the  last  stage  of  our  hints  on  photo- 
graphy at  home,  and  include  a  few  hints  on  the  faking  of 
negatives  and  choice  of  printing  processes.  A  rough  proof 
should  be  taken  from  the  negative  as  soon  as  perfectly  dry,  and 
the  proof  toned  and  fixed  ;  we  are  now  in  a  position  to  find 
faults  and  defects.  If  the  shadow  side  of  the  face  is  too  dark, 
it  will  be  found  advisable  to  coat  the  back  of  the  negative  with 
pale  yellow  matt  varnish,  or  even  to  work  on  the  film  side  with 
a  little  retouching  medium  and  powdered  graphite,  manipulating 
with  a  stump.  Pinholes  may  be  easily  stopped  out  and,  if 
necessary,  a  little  black  speck  on  the  film,  which  gives  a  white 
spot  on  the  print,  can  be  easily  eradicated  by  carefully  manipula- 
ing  a  needle  inserted  in  a  penholder.  Of  actual  retouching,  we 
do  not  intend  to  speak,  further  than  to  strongly  recommend  any 
one  desirous  of  entering  this  by  no  means  difficult  branch  of 
practical  work  to  study  No.  5  of  the  Amateur  Photographer 
handbooks,  and  then  practise  what  is  there  taught.  It  has  been 
said  that  a  successful  retoucher  must  be  an  artist  and  an 
anatomist.  Possibly  this  is  true,  but  any  one  with  a  little 
practice  can  learn  sufficient  retouching  to  be  able  to  soften  down 
glaring  freckles  and  other  defects,  natural  or  appertaining  to  the 
process.  Negatives  should  be  varnished  before  proceeding  to 
actual  printing,  and  although  this  is  too  frequently  a  bugbear  to 
the  amateur,  it  is,  like  everything  else,  merely  a  question  of 
practice.  The  choice  of  printing  process  is  always  a  difficult 
one.  Many  sitters  who  are  ignorant  of  photography  prefer  the 
ordinary  albumen  print,  merely  because  they  have  never  seen 
any  other  process.  For  small  work,  such  as  cartes-de-visite, 
gelatino-chloride  paper,  white  will  give  good  results,  but  for 
larger  work,  such  as  cabinets,  whole-plates,  etc.,  a  matt-surface 
paper  is  far  superior.     To  this  category  belong  matt-surface 

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DICTIONARY  OF  PHOTOGRAPHY. 


[Pot 


chloride  papers,  rough  bromide  paper,  printing-out  platinotype, 
the  ordinary  platinotype,  and  mezzotype.  In  choosing  a  process 
we  must  look  at  the  character  of  the  negative.  Thus  for  a  flat, 
thin  negative  a  gelatino-chloride  paper  should  be  used,  as  this 
tends  to  increase  of  contrast ;  for  a  plucky  negative  with  decided 
contrasts  this  paper  should  be  avoided,  and  a  rapid  bromide  paper 
or  platinotype,  used.  Vignetting  is  by  no  means  difficult,  and,  in 
some  cases,  is  of  advantage  for  cutting  off  unnecessary  details  in 
the  backgrounds,  etc. ;  but  it  should  be  well  done  to  be  effective. 
Then,  again,  the  character  of  the  vignette  should  be  chosen  in 
accordance  with  the  style  and  character  of  the  picture.  Thus,  a 
sitter  in  a  white  dress  against  a  dark  background  should  be  vig- 
netted, not  with  the  margins  white,  which  would  detract  from 
the  high  lights  of  the  picture,  but  the  edges  should  shade  off 
darker,  which  is  obviously  done  by  shading  the  centre  from  the 
action  of  light  and  allowing  the  edges  to  blacken  and  bronze  in 
the  sun.  A  sitter  in  a  dark  dress  against  a  light  background 
may  be  vignetted  in  the  usual  way. 

Positive.  A  reproduction  of  any  object  in  which  the  lights 
and  shades  are  represented  as  seen  in  nature,  whether  on  glass 
or  paper.    It  is  the  opposite  to  Negative  (r/.v.). 

Potassium  Bichromate  (Ger.,'  Kaliumdichromat ;  Fr., 
Bichromate  de  potasse,  Chromate  rouge  de  potassium;  Ital., 
Bichromatadi  potassd).  K2Cra07  =  295.  Synonyms  :  Potassium 
Dichromate,  Red  Chromate  of  Potash,  Acid  Chromate  of  Potash. 
Is  prepared  on  a  large  scale  from  chrome  iron  ore.  It  is  met  with 
commercially  as  fine  orange-red  crystals,  which  give  a  very  deep- 
coloured  solution.  Solubility  ,  7*4  per  cent,  in  cold,  9-4  per  cent, 
in  hot  water  ;  insoluble  in  alcohol.  It  is  of  great  importance 
commercially,  the  fact  of  its  being  decomposed  by  light  when  in 
contact  with  organic  matter  being  taken  advantage  of.  It  is  used 
for  dyeing,  and  also  for  tanning  hides,  the  action  in  this  case 
being  analogous  to  that  in  the  carbon  process.  It  is  used,  photo- 
graphically, for  nearly  every  photo-mechanical  printing  process. 
It  is  also  used  in  solution  as  colour  screens  for  orthochromatic 
work. 

Potassium  Bromide  (Ger.,  Bromkaliumx  Kaliumbrotnid ;  Fr., 
Bromure  de  potassium  ;  Ital.,  Bromuro  di potasio).  KBr=ii9. 
Prepared  in  white  cubical  crystals  by  acting  on  bromide  of  iron 

367 


Pot]  Dictionary  of  photography. 

with  carbonate  of  potash,  or  by  the  action  of  the  metalloid  itsell 
with  caustic  potash,  and  subsequent  purification  and  crystallisa- 
tion. Solubility :  58  per  cent,  in  cold,  102  per  cent,  in  hot  water ; 
0*13  per  cent,  in  cold,  7  per  cent,  in  boiling  alcohol;  0-2  per  cent, 
in  ether,  0-05  alcohol  and  ether  ;  25  per  cent,  in  glycerine. 

Potassium  Carbonate  (Ger.,  Kaliumcarbonat,  Kohlensaures 
Kali,  Potasche ;  Ft.,  Carbonate  de  potasse ;  Ital.,  Carbonato  di 
potassd).  K2C03,3H20  =  192.  Synonyms:  Pearlash,  Subcarbon- 
ate  of  Potash,  Salt  of  Tartar,  Salt  of  Wormwood,  Potash.  It 
contains  nearly  always  about  16  per  cent,  of  water  of  crystallisa- 
tion, and  is  prepared  by  lixiviation,  and  subsequent  purification, 
of  the  ashes  of  wood  and  vegetable  matters.  Solubility :  100  in 
75  of  water;  insoluble  in  alcohol  and  ether.  It  is  extremely 
deliquescent — that  is,  absorbing  moisture  from  the  air — and 
becomes  a  pasty  mass.  It  is  used  for  developing,  and  for  the 
preparation  of  the  other  salts  of  potash.  It  should  not  be  con- 
founded with  the  bicarbonate  or  acid  carbonate  of  potash 
(KHCO3),  which  is  a  much  less  active  salt. 

Potassium  Chloroplatinite  (Ger.,  Kaliumplatinchlorur,  Pla- 
tinkaliumchlorur  ;  Fr.,  Chloroplatinite  de  potassium;  Ital., 
Cloroplatinito  di  potassid).  K2PtCl4  =  318-6.  This  is  prepared 
by  heating  50  parts  of  bichloride  of  platinum  dissolved  in  100 
parts  of  water  to  ioo°  C,  and  passing  through  it  a  stream  of 
washed  sulphurous  anhydride,  S02,  till  the  solution  turns  deep 
red,  and  gives  no  precipitate  with  ammonium  chloride.  The 
solution  is  then  allowed  to  cool,  and  25  parts  of  potassium 
chloride  in  50  parts  of  water  added,  and  the  solution  allowed  to 
crystallise,  and  the  crystals  washed.  It  may  also  be  prepared  by 
mixing  cuprous  chloride  and  potassio-chloride  of  platinum  into 
a  paste  with  water,  and  dissolving  the  resulting  chloroplatinite 
out  with  water  and  crystallising  ;  also  by  mixing  47  parts  of 
caustic  potash  with  120  parts  of  platinum  perchloride.  It  occurs 
in  ruby  red  deliquescent  crystals,  very  soluble  in  water,  insoluble 
in  alcohol.  It  is  used  in  platinotype  printing  and  for  toning 
prints.  A  convenient  method  of  preparing  this  salt  for  the 
platinotype  process  is  that  given  by  Hoffman  : — Take  of  platinum 
in  scraps  5  parts,  dissolve  in  aqua  regia,  and  evaporate  carefully 
till  the  solution  is  sirupy ;  add  5  parts  of  potassium  chloride  dis- 
solved in  a  little  distilled  water ;  then  evaporate  down  till  it 

368 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pot 


forms  a  mass.  Dissolve  the  mass  in  sufficient  water  to  make  100 
parts.  To  the  100  parts  of  this  solution  add  10  parts  of  dry- 
ferrous  oxalate,  and  heat  in  a  capsule  for  about  two  minutes  at 
1580  F.,  and  allow  to  cool  and  filter.  Double  decomposition 
takes  place,  and  a  mixture  of  ferric  oxalate  and  chloroplatinite  is 
formed. 

Potassium  Cyanide  (Ger.,  Cyankalium,  Kaliumcyanid';  Fr., 
Cyanurc  de  potassium  ;  Ital.,  Cianuro  di potassio.  KCN  or  KCy 
=  65.  Synonyms:  Cyanide  of  Potash,  Cyanide.  Obtained  by 
fusing  ferrocyanide  of  potassium  with  carbonate  of  potash.  The 
resulting  fluid  mass  is  poured  out  on  slabs,  and  then  broken  up 
into  the  irregular  masses  met  with  in  commerce.  Solubility. 
1  in  1  of  cold,  122  per  cent,  in  hot  water;  1*2  per  cent,  in  abso- 
lute alcohol ;  more  soluble  in  dilute  alcohol.  It  is  used  for 
reducing  the  density  of  negatives,  and  for  fixing  in  the  wet 
process.  It  is  extremely  poisonous  when  taken  internally,  and 
also  when  absorbed  through  the  skin,  or  by  any  cut  or  abrasion. 
The  addition  of  an  acid  immediately  causes  the  evolution  of 
hydrocyanic  or  prussic  acid  gas,  which  is  extremely  poisonous, 
and  when  inhaled,  even  in  small  quantities,  produces  vertigo  and 
headache. 

Potassium  Ferricyanide  (Ger„  Rothes  Blutlaugensah, 
Kaliumeisencyanid ;  Fr.,  Ferricyanure  de  potassium,  Cyanoferride 
de  potassium,  Prussiate  rouge  de  potassium  ;  Ital.,  Cianuro  rosso 
di  potassio  e  diferro,  Prussiato  rosso  di  potassio.  K6Fe.,(CN)!, 
=  658.  Synonyms  :  Ferridcyanide  of  Potash,  Red  Prussiate  of 
Potash.  Made  by  the  action  of  chlorine  gas  on  ferrocyanide  of 
potash.  Solubility  :  36  per  cent,  in  cold,  776  per  cent,  in  hot 
water ;  insoluble  in  absolute  alcohol ;  more  soluble  in  dilute 
alcohol.  It  is  met  with  as  deep  red  crystals,  that  become 
covered  with  a  yellowish  powder,  which  should  be  removed  by 
rinsing  with  water  before  use.  It  is  used  for  reducing,  and  in 
some  printing  processes,  also  for  toning  bromide  prints. 

Potassium  Ferrocyanide  (Ger.,  Gelbes  Blutlauge?isalz, 
Kaliumeisencyaniir ;  Fr.,  Ferrocyanure  de  potassium,  Prussiate 
jatcne,  Cyanoferrure  de  potassium  ;  Ital.,  Cianuro  giaito  di  potassio 
e  diferro,  Prussiato  giallo  di  potassio).  K4Fe(CN)6,  3rl,0  =  426. 
Synonym  :  Yellow  Prussiate  of  Potash.  Is  prepared  by  heating 
nitrogenous  matter,  such  as  hoofs,  horns,  hide  clippings,  etc.,  with 

369  B  li 


Pot] 


DICTIONARY  OF  PHOTOGRAPHY. 


pearlash  and  iron  filings  in  an  iron  pot.  The  resulting  mass  is 
dissolved  in  water  and  evaporated,  and  the  large  yellow  plates  or 
crystals  of  the  salt  obtained.  Solubility  :  26  per  cent,  in  cold,  50 
per  cent,  in  hot  water ;  insoluble  in  alcohol.  The  salt  is  non- 
poisonous  of  itself;  but  as  a  deadly  poison  can  be  easily  prepared 
from  it,  care  should  be  exercised  in  its  use.  It  has  been  recom- 
mended as  an  addition  to  developers,  and  is  said  to  give  pluck 
and  brilliancy  to  the  negatives. 

Potassium  Iodide  (Ger.,  Iodkalium,  Kaliumiodid ;  Fr.,  Iodure 
de  potassium ;  Ital.,  Ioduro  di  potassio.)  KI  =  166.  Prepared 
by  dissolving  iodine  in  hot  solution  of  caustic  potash,  evaporating 
and  fusing  the  crystalline  mass  with  charcoal,  and  subsequent 
lixiviation.  Solubility:  138  per  cent,  in  cold,  220  per  cent,  in 
hot  water;  1*5  per  cent,  in  alcohol,  0*12  per  cent,  in  ether 
o-8  per  cent,  in  alcohol  and  ether;  40  per  cent,  in  glycerine. 
It  is  used  for  iodising  collodion,  in  emulsion  making  and  as  an 
ingredient  of  some  intensifies. 

Potassium  Metabisulphite  (Ger.,  Kaliummetabisulfit ;  Fr., 
Metabisulfite  de  potassium,  Bisulfite  or  Sulfite  acide  de  potasse  ; 
Ital.,  Metabisolfito  di  potassa).  K2S205  =  2-32.  Prepared  by 
saturating  solution  of  potassium  carbonate  with  sulphurous  acid 
gas  and  precipitating  the  metabisulphite  with  alcohol.  Solubility  : 
1 :  3  of  water,  insoluble  in  alcohol.  It  is  used  as  a  preservative  of 
pyrogallol,  but  on  keeping  becomes  very  acid  and  necessitates 
therefore  the  use  of  larger  quantities  of  alkali.  It  may  also  be 
used  as  an  addition  to  the  fixing  bath  to  make  the  same  acid 
and  prevent  it  staining.  . 

Potassium  Nitrate  (Ger.,  Salpetersaures  Kali,  Kaliumnitrat, 
Salpeter,  Kalisalpeter ;  Fr.,  Azotate  de  potasse,  Nitrate  de  potasse, 
Salpetre  set  de  nitre  ;  Ital.,  Azotato  di  potassa).  KN03  =  101. 
Synonyms :  Nitre,  Saltpetre.  Occurs  naturally  in  many  parts  of 
India,  contaminated  with  nitrate  of  calcium.  It  is  also  made 
artificially  by  the  process  of  nitrification.  It  can  also  be  made  by 
adding  chloride  of  potash  to  nitrate  of  sodium  in  solution.  Solu- 
bility :  30  per  cent,  in  cold,  335  per  cent,  in  hot  water ;  insoluble 
in  cold  alcohol,  2  per  cent,  in  boiling  alcohol.  It  is  used  for 
making  nitric  acid,  pyroxylin  and  for  magnesium  flashlight 
powders. 

370 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pot 


Potassium  Nitrite  (Ger.,  Salpetrigsaures  Kali,  Kaliumiiitrit ; 
Fr.,  Azotite  de potassium  ;  ItaL,  Azotito  di potassio).  KN02=85. 
Can  be  made  by  heating  nitrate  of  potassium,  when  oxygen  is 
given  off  and  the  nitrite  left.  It  is  an  extremely  deliquescent 
salt,  and  of  but  little  use  photographically,  it  being  recommended 
for  preparing  the  paper  for  Actinometers  (q.v.),  and  for  preventing 
commercial  sensitised  paper  from  yellowing. 

Potassium  Oxalate  (Ger.,  Oxalsdures  Kali,Kaliumoxalat;  Fr., 
Oxalate  neutre  de  potassium ;  ItaL,  Ossalato  neutro  di  potassd). 
K.,CX)4  =  164.  Synonym  :  Neutral  Oxalate  of  Potash.  Pre- 
pared by  neutralising  oxalic  acid  with  carbonate  of  potash  or 
caustic  potash.  Solubility :  1  in  3  of  water  ;  insoluble  in  alcohol 
or  ether.  It  is  used  for  the  production  of  ferrous  oxalate,  and  as 
a  developer  in  the  platinotype  process.  A  convenient  method  of 
making  it  is  as  follows  : — Dissolve  13  ozs.  of  carbonate  of  potash 
in  30  ozs.  of  water,  and  add  gradually  about  9  ozs.  of  oxalic  acid, 
till,  after  boiling,  the  solution  is  neutral  to  test  paper.  Filter  and 
make  the  resulting  solution  measure  64  ozs.,  when  a  solution  of 
oxalate  of  potash  will  be  obtained  1  in  4.  This  salt  should  not 
be  confounded  with  the  binoxalate  or  acid  oxalate  of  potash  known 
commercially  as  salt  of  sorrel,  from  which  it  may  be  prepared  by 
heating  200  parts  of  acid  oxalate  in  1000  parts  of  water,  and  add- 
ing carbonate  or  bicarbonate  of  potassium,  till  a  faint  alkaline 
reaction  is  given,  and  then  adding  a  few  grains  of  oxalic  acid  or 
the  acid  salt. 

Potassium  Permanganate  (Ger.,  Ubernuui^a/isiiures  Kali, 
Kaliumhypermanganat ;  Fr.,  Per?nanganate  de  potasse,  Cameleo7i 
mineral;  ItaL,  Permanganate  di  potassd).  K.MnX).,  =  1 58. 
Prepared  by  fusing  together  hydrate  and  chlorate  of  potash  and 
black  oxide  of  manganese,  boiling  the  product  thus  obtained  with 
water,  and  purifying  and  crystallising  the  product.  Solubility  : 
6-3  per  cent,  in  cold,  very  soluble  in  hot  water ;  decomposed  by 
alcohol.  It  is  used  for  intensifying  negatives,  as  a  test  for  hypo, 
and  as  an  intensifier  for  carbon  prints. 

Potassium  Sulphide  (Ger.,  Schwefelkalium,  Kaliumsulfid 
Schwefelleber ;  Fr.,  Foie  de  soufre,  Trisulfure  de  potassiui?i  ; 
ItaL,  Pentasulfuro  di  potassio).  K^C^K^):,.  Synonyms : 
Liver  of  Sulphur,  Sulphurated  Potash,  Potassium  Trisulphide. 

371 


Pot] 


DICTIONARY  OF  PHOTOGRAPHY. 


Made  by  heating  together  sulphur  and  carbonate  of  potash,  the 
resulting  mass  being  poured  out  on  slabs  and  broken  up.  It 
usually  consists  of  one  molecule  of  hyposulphite,  K2S203,  and  two 
molecules  of  sulphide,  K2S3.  Solubility :  partially  soluble  in 
water,  and  three-quarters  of  it  by  weight  soluble  in  alcohol.  It 
is  used  for  the  reduction  of  residues. 

Powder  Process.  A  process  much  used  on  the  Continent 
for  the  production  of  prints  on  paper,  and  in  England  for  trans- 
parencies on  glass.  The  process  is  not  by  any  means  difficult, 
and  as  the  results  are  extremely  pleasing  and  can  be  obtained 
in  any  colour,  the  process  is  well  worth  the  attention  of  amateurs. 
An  organic  tacky  body,  sensitised  with  bichromate  of  potash 
or  ammonia,  is  allowed  to  dry  as  much  as  possible,  and  exposed 
to  light,  when  it  is  found  that  the  tackiness  of  the  organic  body 
disappears  in  exact  proportion  to  the  action  of  light,  and  any 
fine  powder  dusted  on  will  adhere  to  the  tacky  portions  unacted 
upon  by  light.  It  is  obvious,  therefore,  that  by  this  means  an 
image  can  be  obtained  in  any  colour,  and  almost  any  material,  a 
reversed  positive  being  used  to  produce  a  positive.  It  has  been 
lately  recommended  in  the  Amateur  Photographer  iox  the  pro- 
duction of  lantern  slides,  and  from  experiments  made  by  the 
author  seems  very  suitable  for  the  purpose.  The  following 
formulae  are  recommended  for  the  preparation  of  the  organic 
tacky  body  : — 

Obernetter's  Formula. 

Dextrine   60  grs.    or    4  grms. 

White  sugar    75  „       „     5  „ 

Ammonium  bichromate    ...    30  „       ,,     2  ,, 
Glycerine       2  to  8  mins.  or  -06  to  5  c.cm.  to  -28  c.cm. 
Distilled  water    3  ozs.  or  100  c.cm. 

Woodbury's  Formula. 

Gum  arabic   60  grs.    or    4  grms. 

Glucose   45   „       „    3  „ 

Glycerine   10  mins.  ,,  o*5  c.cm. 

Potassium  bichromate  ...  30  grs.  ,,  2  grms. 
Distilled  water    2  ozs.     „  50  c.cm. 


Mix  by  gently  heating,  filter,  and  preserve  in  a  stoppered  bottle 

372 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pri 


A  plate  is  coated  with  either  of  the  above  solutions,  and  dried  at 
a  gentle  heat,  and  then  exposed  under  a  positive,  reversed  as 
regards  left  and  right,  for  three  or  five  minutes  to  sunlight,  or 
ten  or  fifteen  minutes  to  diffused  light ;  on  removal  from  the 
printing-frame  a  faint  image  is  seen.  The  plate  is  then  exposed 
to  the  air  for  a  few  minutes  to  allow  it  to  absorb  moisture,  and 
fine  plumbago,  as  used  by  electrotypers,  is  applied  with  a  flat 
brush,  when  it  adheres  to  those  portions  protected  from  light, 
and  the  lights  and  shades  are  represented  more  or  less  by  a 
coating  of  graphite.  When  the  image  is  fully  developed,  and 
there  is  no  further  adherence  of  the  graphite,  the  superfluous 
powder  is  dusted  off,  the  film  is  coated  with  collodion,  and  then 
well  washed  to  remove  the  unacted-upon  gum  and  bichromate  ; 
the  film  may  be  detached  from  the  plate,  and  used  for  enamels, 
ivory,  opal,  or  any  textile  fabric. 

Primuline  (Ger.,  Primulin;  Fr.,  Primiilin;  Ital.,  Primulina). 
A  complex  organic  dye  obtained  by  the  action  of  sulphur  and 
fuming  sulphuric  acid  on  paratoluidin.  It  has  the  property  of 
dyeing  cotton  without  any  mordant,  and  is  used  in  the  Diazotype 
process. 

Primuline  Process.   See  Diazotype  Printing. 

Principal  Axis  is  the  straight  line  which  joins  the  centres  of 
curvature  of  the  spherical  surfaces  of  a  lens,  or  if  one  surface  is 
plane,  the  principal  axis  passes  through  the  centre  of  curvature 
of  the  spherical  surface,  and  perpendicular  to  the  plane  surface. 
A  straight  line  passing  through  the  optical  centre,  and  making 
an  angle  with  the  principal  axis,  is  termed  a  secondary  axis. 
The  centres  of  curvature  are  the  points  from  which  the  arcs 
of  the  circles  forming  the  spherical  surfaces  of  the  lenses  arc- 
calculated — that  is,  the  centres  of  curvature  are  the  centres 
of  circles,  of  which  circles  the  spherical  surfaces  of  the  lens 
are  segments. 

Printing.  This  term  is  applied  to  any  method  by  means  of 
which  a  positive  is  obtained  from  a  negative,  or,  in  fact,  a 
picture  is  obtained  in  which  to  some  extent  at  least  the  gradations 
of  light  and  shade  are  represented  as  seen  in  nature.  More 
usually,  however,  this  term  includes  the  production  of  pictures 

373 


Pri]  DICTIONARY  OF  PHOTOGRAPHY. 

upon  any  flexible  support,  such  as  paper ;  and  as  the  other 
branches  of  printing,  such  as  bromide  paper,  opals,  and  lantern 
slides  by  means  of  which  prints  are  obtained  by  development, 
are  treated  of  elsewhere,  it  is  the  author's  intention  to  confine 
this  article  entirely  to  what  is  termed  sensitised  or  albumenised 
paper  printing.  If  the  operator  desires  to  sensitise  his  own  paper, 
instructions  will  be  found  elsewhere,  and  it  is  supposed  that  he 
has  his  paper  ready  for  cutting  to  the  desired  size.  The  author 
would  impress  upon  his  readers  the  necessity  for  cutting  the  paper, 
not  to  the  exact  size  of  the  finished  print,  but  rather  larger.  He 
recommends  the  use  of  an  old  negative  glass  for  cutting  it  to 
shape,  as  this  allows  of  some  margin,  and  does  not  require 
such  nice  adjustment  as  when  the  paper  is  cut  to  the  exact  size. 
Having  the  paper  ready  cut,  the  next  operation  is  to  place  it  in 
the  printing-frame.  This  should  be  done  in  weak  daylight,  and 
the  film  side  of  the  negative  should  be  placed  next  to  the  paper, 
and  one  or  two  thicknesses  of  blotting  paper  placed  on  the  back 
of  the  paper,  the  hinged  back  being  put  into  position,  and  the 
springs  fastened  down.  The  next  question  which  naturally 
arises  is  that  of  light :  what  light  is  the  best  to  print  in  ?  On 
this  point  there  can  be  no  doubt ;  except  during  the  months 
of  November,  December,  January,  and  February,  and  in  the  case 
of  very  dense  negatives,  sunshine  should  never  be  used.  Some 
authorities  recommend  printing  in  the  sun  with  a  screen  of 
tissue  paper  over  the  negative,  but  even  in  this  case  the  author 
thinks  better  effects  are  obtained  by  printing  in  the  shade.  Select, 
if  possible,  a  window-sill  or  other  open  space,  which  has  a  free, 
uninterrupted  view  of  the  sky,  and  place  the  printing-frame  out 
and  leave  for  a  short  time  ;  then  withdraw  into  a  subdued  light,  and, 
unfastening  one  of  the  springs,  turn  back  the  half  of  the  back  and 
examine  the  paper.  Some  may  think  the  caution  of  examining 
the  print  in  subdued  light  unnecessary  ;  but  it  is  not.  By  examin- 
ing the  paper  in  a  strong  light  the  purity  of  the  whites  is  degraded, 
and  a  decided  tinge  given  to  them.  For  printing  from  weak  thin 
negatives  a  screen  of  tissue  paper  is  an  advantage,  or  the  back  of 
the  negative  may  be  coated  with  matt  varnish  or  ordinary  negative 
varnish,  tinted  with  gamboge,  aurantia,  or  some  other  yellow 
dye.  For  very  dense  negatives,  as  stated  above,  printing  in  the 
sun  is  allowable.  When  a  negative  is  very  dense  at  one  end  and 
not  at  the  other,  the  printing-frame  may  be  placed  in  a  deep 

374 


DICTIONARY  OF  PHOTOGRAPHY. 


[Pri 


lidless  box  resting  up  against  one  side,  with  the  denser  end 
uppermost ;  by  this  means  the  printing  may  to  some  extent  be 
equalised.  The  next  question  is  how  dark  or  to  what  depth 
the  printing  should  be  carried.  On  this  point  considerable 
difference  of  opinion  exists,  it  being  to  some  extent  dependent 
upon  what  toning  bath  is  used,  as  some  baths  bleach  more  than 
others ;  but  as  a  rule,  for  general  guidance,  printing  should  be 
carried  on  till  the  whites  of  the  pictures  are  well  coloured  and 
the  shadows  beginning  to  block  up.  Prints  should  not  be  kept  too 
long  before  being  toned,  as  some  further  chemical  change  takes 
place,  and  discoloration  of  the  paper  ensues,  and  it  is  then  almost 
impossible  to  tone  satisfactorily,  if  at  all,  by  any  of  the  ordinary 
baths.  There  is  one  process  in  photographic  printing  in  which 
at  least  considerable  artistic  skill  is  required — viz.,  combination 
printing,  by  means  of  which  at  least  we  may  to  some  extent 
utilise  the  material  already  found,  and,  employing  some  of  the 
licence  of  artists  of  the  brush  and  palette,  produce  effects  which 
are  not  strictly  true,  but  are  yet  more  artistic.  Thus,  in  the  case 
of  a  low-lying  horizon,  the  uniform  tint  of  the  sky  is  extremely 
unnatural  and  really  untruthful,  as  we  never  hardly  find  in  nature 
a  sky  so  barren  of  clouds  or  colours  as  to  present  one  uniform 
unbroken  tint,  as  given  by  the  agency  of  the  camera  and  dry  plate. 
In  such  a  case  the  sky  may  be  graduated  in  tint  from  pure  white 
at  the  horizon  to  a  deeper  tint  in  the  zenith,  or  we  may  have 
recourse  to  a  second  negative,  and  print  in  some  fine  masses  of 
clouds.  The  author  has  in  his  possession  a  print  of  a  bit  of  an 
Essex  marsh,  as  flat  and  as  uninteresting  in  itself  as  it  is  possible 
for  anything  to  be,  but  the  whole  has  been  converted  by  means 
of  a  cloud  negative  into  one  of  the  finest  pictures  it  is  possible 
to  produce,  the  clouds  giving  one  the  impression  of  a  dull,  windy 
day  in  autumn,  in  which  the  cattle  huddle  together  and  turn 
their  backs  to  the  gale,  and  man  instinctively  buttons  up  his 
coat  and  bends  his  head  to  the  wind.  It  is,  I  think,  as  clever 
and  suggestive  in  its  way  as  any  of  the  grand  compositions  of 
J.  W.  M.  Turner,  perhaps  the  only  true  artist  who  could  depict 
wind  and  clouds.  Again,  by  use  of  a  second  negative  a  figure  may 
be  introduced  into  an  otherwise  uninteresting  stretch  of  country, 
giving  life  and  beauty  to  the  whole,  and  raising  the  composi- 
tion at  once  above  the  mediocre  photograph.  To  effect  such 
composition  requires  true  artistic  skill  and  considerable  clever 

375 


Pyr] 


DICTIONARY  OF  PHOTOGRAPHY. 


manipulation  in  a  photographic  sense.  The  usual  method  of 
making  such  an  effect  is  to  print  the  subject,  such  as  a  stretch  of 
land,  first,  and  to  utilise  this  print  as  a  mask.  For  this  purpose 
the  outlines  must  be  carefully  cut  out  with  a  pair  of  scissors,  and 
after  a  second  print  has  been  taken,  to  place  the  first  and  cut-out 
mask  over  the  second  print,  and  place  on  top  of  it  the  cloud  or 
second  negative,  and  again  expose  to  light  till  the  second 
negative  has  printed  in  sufficiently  deep.  Another  method  is  to 
paint  over  the  first  print  with  gamboge  or  some  other  non- 
actinic  paint,  and  print  again  under  the  second  negative  when 
dry.  This  method,  however,  is  not  so  satisfactory.  For  tinting 
the  skies  a  piece  of  sheet  tin  or  stout  cardboard  should  be  used, 
and  one  end  bent  up  to  about  an  angle  of  45  degs.  This  can  be 
placed  over  the  print,  and  the  whole  exposed  to  daylight,  the 
metal  or  cardboard  being  moved  up  or  down,  so  as  to  graduate 
the  tinting.  It  is  only  by  practice  that  success  in  this  branch  of 
printing  can  be  obtained,  the  chief  difficulty  being  to  so  blend 
the  print  from  the  two  negatives  as  to  show  not  the  slightest 
trace  of  the  use  of  two  negatives.  (For  further  considerations  in 
respect  of  printing,  the  reader  is  referred  to  Abney  and  Robin- 
son's "  Photographic  Printers' Assistant ;  "  and  "  Silver  Printing," 
by  W.  M.  Ashman.) 

Pyrogallic  Acid  (Ger.,  Pyrogallussaure ;  Fr.,  Acide  Pyro- 
gallique).  QH603  =  26.  Is  not  actually  an  acid,  its  proper 
chemical  name  being  pyrogallol ;  it  is  prepared  by  sublimation 
from  gallic  acid.  In  the  presence  of  alkalies  in  solution  it  absorbs 
oxygen  from  the  air,  turning  black,  a  carbonate  and  acetate  of 
the  alkali  used  being  formed.  It  is  a  powerful  deoxidiser  and 
reducing  agent,  and  is  more  extensively  used  than  any  other  agent 
for  developing.  As  pyro  is  very  easily  oxidised  it  is  extremely 
difficult  to  preserve  in  solution,  many  substances  being  recom- 
mended for  that  purpose  ;  the  following  are  some  of  them,  which 
are  enumerated  in  the  order  of  their  value  for  that  purpose : — 
A  mixture  of  glycerine  and  alcohol,  metabisulphite  of  potash, 
sulphite  of  soda,  citric  acid.  Solubility :  1  in  2  of  water,  the 
resulting  solution  measuring  i\ ;  9  in  10  of  alcohol ;  it  is  also 
soluble  in  glycerine  and  ether. 

Pyroxylin  (Ger.,  Pyroxylin,  Collodiumwolle,  Scheissbaum- 
wolle ;  Fr.,  Pyroxyle ;  Ital.,  Cotone  Fulminante,  Pirossilind).  A 

376 


DICTIONARY  OF  PHOTOGRAPHY.  [PyT 

substance  of  variable  composition  obtained  by  acting  upon 
cellulose  C6H10O5,  with  a  mixture  of  nitric  and  sulphuric  acids, 
and  in  this  process  one  or  more  atoms  of  hydrogen  are  replaced 
by  NOa.  The  following  directions  for  preparing  it  are  taken 
from  Hardwich's  "  Photographic  Chemistry,"  but  the  author 
would  advise  anybody  who  requires  small  quantities  to  buy  it 
ready  made,  rather  than  prepare  it  for  their  own  use,  as  the 
operation  is  not  very  easy,  and  the  acids  are  dangerous  to 
handle : — 

Sulphuric  acid   (sp.  gr., 

1-854  at  6o°  F.)    18  fluid  ozs.  or  500  c.cm. 

Nitric  acid  (sp.  gr.,  1*457 

at6o°  F.)  ...    6  1  „      „    „  166  „ 

Distilled  water    4f  ,,      ,,     ,,  140  ,, 

Pour  the  water  into  a  dish,  add  the  nitric  acid,  and  lastly  the 
sulphuric  acid.  The  mixture  must  be  well  stirred,  and  the 
temperature,  which  is  raised  by  the  addition  of  the  sulphuric 
acid,  should  be  allowed  to  sink  to  1500  F.,  at  which  heat  the 
mixture  must  be  kept  by  means  of  a  water  bath.  The  wool  must 
be  first  put  in  a  strong  solution  of  carbonate  of  soda  or  potash 
to  free  it  from  its  natural  oil,  and  then  washed  in  plain  water 
till  the  washings  show  not  the  slightest  trace  of  alkalinity  or 
the  salt  used,  and  dried.  The  prepared  wool  should  be  then 
weighed  out  into  balls  of  about  thirty  grains  each,  and  immersed 
one  by  one  into  the  mixture  of  acids,  and  well  stirred  up,  care 
being  taken  that  each  little  ball  is  thoroughly  saturated  with 
acid ;  they  should  be  left  for  ten  minutes,  and  then  taken  out 
and  washed  in  running  water  for  twenty-four  hours,  or  till  they 
show  no  acid  reaction  with  litmus ;  they  can  be  then  dried 
in  the  sun,  or  on  a  water  bath.  The  resulting  production  should 
be  entirely  soluble  in  a  mixture  of  equal  parts  of  alcohol  and 
ether,  and  also  inflammable.  The  nitric  acid  alone  acts  upon 
the  cotton,  the  sulphuric  causing  this  action  to  be  much  more 
rapid.  This  action  of  the  sulphuric  acid  is  said  to  be  catalytic. 
A  special  kind  of  pyroxyline,  called  celloidin,  has  been  introduced 
by  Dr.  Schering,  of  much  greater  purity  than  the  other,  and 
which  yields  a  much  finer  collodion.  This  is  said  to  be  prepared 
by  immersing  ordinary  pyroxyline  in  pure  nitric  acid  for  ten 
minutes,  washing  and  drying.    Pyroxyline  is  insoluble  in  water, 

377 


Rap] 


DICTIONARY  OF  PHOTOGRAPHY 


alcohol,  and  ether,  but  soluble  in  a  mixture  of  the  two  latter, 
and  also  in  glacial  acetic  acid.   It  is  used  for  preparing  collodion. 

Rapidity  of  Lenses.  The  rapidity  of  a  lens  depends  upon 
the  relation  the  working  aperture  bears  to  the  focus.  It  is  an 
almost  universally  misunderstood  question.  Because  a  lens- 
maker  calls  one  lens  rapid  rectilinear,  it  is  generally  supposed 
that  such  a  lens  is  the  quickest  and  most  suitable  for  in- 
stantaneous or  general  work,  whereas  what  is  termed  a  wide- 
angle  may  be  equally  as  rapid  with  the  same  size  diaphragm, 
which  gives  the  same  working  aperture.  The  following  rule  is 
a  standard  on  this  point :  "  Depth  of  focus  and  definition  are 
opposed  to  rapidity.  Whatever  increases  the  rapidity  of  a  lens 
reduces  the  power  of  definition,  and  conversely  any  gain  in 
definition  and  depth,  granting  the  lens  to  be  well  made  in  other 
respects,  must  be  made  at  the  expense  of  rapidity."  Definition 
and  depth  are  thus  opposed  to  rapidity.  As  rapidity  is  increased 
with  larger  aperture,  definition  and  depth  are  lost,  till  a  point  is 
reached  at  which  the  extent  of  such  loss  prevents  the  further 
increase  of  rapidity.  Supposing  a  lens  is  being  used  which 
works  at  //8,  and  it  is  desired  to  substitute  a  lens  working  at 
fl 22,  and  the  exposure  for  a  given  subject  is  known  with  the 
former,  the  increase  of  exposure  is  found  by  squaring  and  com- 
paring these  numbers:  //8  X  8  =  64, //22  x  22  =  484.  There- 
fore the  exposure  will  be  as  64  to  484,  or  1  to  7-5.  In  this  way 
the  necessary  increase  in  exposure  for  any  size  aperture  may  be 
found. 

/////      /        /  // 
42     62     82     n-32  162    222      32s     452  642 
16    36    64     127     256    484    1,024  2,025  4»096 

Or  reducing  these,  and  reckoning  the  exposure  necessary  with 
/J 4  as  unity,  the  exposures  will  be — 1,  2*25,  4,  7-9,  16,  30*25,  64, 
126*5,  256. 

Rapid  Rectilinear.   See  Lens. 

Reaumur.    See  Thermometer. 

Redevelopment.  A  process  usually  confined  to  the  wet 
collodion.  It  is  actually  intensification  of  the  image.  It  has 
been  suggested,  however,  for  dry  plates  and  bromide  papers, 

378 


DICTIONARY  OF  PHOTOGRAPHY. 


[Red 


and  is  useful  in  the  former  case  to  intensify  under-developed 
negatives,  and  in  the  latter  to  obtain  warmer  tones.  The  negative 
to  be  intensified  is  washed  thoroughly  free  from  hypo,  and 
bleached  in  a  solution  of  cupric  or  mercuric  chloride,  well 
washed,  and  then  redeveloped  with  hydroquinone  or  ferrous 
oxalate.    To  make  a  solution  of  cupric  chloride  : — 

Solution  I. 

Chloride  of  calcium  (crystalline)  147  grs.  or  10  grms. 
Distilled  water  ...       ...       ...       2  ozs.    ,,  60  c.cm. 

Solution  II. 

Sulphate  of  copper  249  grs.    or  1 5  grms. 

Distilled  water   10  drms.  ,,  40  c.cm. 

Dissolve  each  separately,  mix,  and  filter.  For  obtaining  warm 
tones  with  bromide  paper,  the  finished  print  is  bleached  as 
above,  and  then  redeveloped  with  hydroquinone  or  dilute  ferrous 
citrate  developer.  To  obtain  a  regular  tone  it  has  been  recom- 
mended to  bleach  Alpha  paper  with  mercuric  chloride,  and 
redevelope  with  ferrous  oxalate.  A  process  of  redevelopment 
suggested  by  Mr.  B.  J.  Edwards  is  given  under  Development. 

Red  fog.    See  Fog. 

Reduction  (in  Size).  An  exceedingly  useful  operation  in 
the  preparation  of  lantern  slides  or  prints  from  larger  sized 
negatives.  One  or  two  methods  may  be  adopted,  both  of  which 
are  satisfactory — one  for  daylight,  the  other  for  artificial  light ; 
and  the  arrangements  suggested  for  enlarging  with  some  modi- 
fications will  do.  The  negative  to  be  reduced  in  size  should  be 
placed  in  the  same  position  (see  Enlargement),  but  in  this  case 
the  lens  is  turned  towards  the  negative,  and  focussed  on  the 
ground-glass  screen  in  the  usual  way.  The  distance  between 
the  negative  and  the  lens  may  be  found  by  referring  to  the  table 
given  under  Enlargement,  or  the  same  rules  there  given  may 
be  used  for  finding  the  distances,  only  they  must  be  reversed — 
that  is,  whereas  in  enlargements  the  greater^distance  is  between 
lens  and  sensitive  surface,  in  the  case  of  reduction  the~  greater 
distance  must  be  between  the  lens  and  negative,  and  the  lesser 
between  lens  and  sensitive  plate. 

379 


DICTIONARY  OF  PHOTOGRAPHY. 


Reduction  of  Density.  When  a  negative  or  print  has  been 
over-developed  or  over-printed,  the  following  processes  may  be 
adopted  for  reducing  them  : — 

Reduction  of  Negatives.  Howard  Farmer's  Reducer.  This 
was  suggested  by  Howard  Farmer  in  1883.  Make  a  10  per 
cent,  solution  of  ferridcyanide  of  potassium,  immerse  the 
negative  which  should  preferably  have  been  dried  in  a  1  : 8 
solution  of  hypo,  and  then  add  a  few  drops  of  the  ferridcyanide 
reducer,  and  carefully  watch  the  action,  taking  the  negative  from 
the  solution  before  quite  reduced  to  the  desired  degree.  The 
more  ferridcyanide  added,  the  stronger  and  quicker  the  action ; 
when  only  a  little  ferridcyanide  is  used,  the  action  proceeds 
slowly  and  the  gradation  does  not  suffer,  with  larger  quantities 
the  shadows  can  be  eaten  away  and  the  contrasts  increased. 

Belitski's  Reducer.  This  is  the  most  convenient  as  it  is  one 
solution,  will  keep  in  the  dark  indefinitely,  can  be  used  over  and 
over  again,  and  when  inactive  and  exhausted  the  colour  changes. 

Potassium  ferric  oxalate    22  grs.  or  10  grms. 

Sodium  sulphite      ...       ...       ...    18   „    „    8  ,, 

Water...       ...       ...       ...       ...      1  oz.  or  200  c.cm. 

When  dissolved  add — 

Oxalic  acid    ...       ...       ...       ...      3  grs.  or  2^  grms. 

and  shake  till  the  blood-red  solution  turns  green ;  decant  from 
any  undissolved  acid,  then  add — 

Sodium  hyposulphite         ...       ...    120  grs.  or  50  grms. 

Dissolved  in 

Water  ...       ...       ...       ...       \  oz.  or  100  c.cm. 

This  can  be  applied  immediately  after  fixing  or  to  a  previously 
dried  negative,  and  causes  no  stain. 

Eau  de  Javelle.    The  method  of  using  this  is  as  follows  : — 

Solution  I. 

Chrome  alum    20  grs.  or  1*3  grms. 

Distilled  water     ...       ...       ...       1  oz.   ,,    25  c.cm. 

Solution  II. 
Eau  de  Javelle  or  Labarraque's  Solution 
380 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ref 


The  Reducer. 

Solution  I.  ...       ...       ...  ^  oz.  or  12  5  c.cm. 

rl       H   <J  m     »  „ 

Water    5  „  ,,150 

This  mixture  is  first  of  a  thick  green  colour,  and  then  turns  to  a 
clear  yellow.  If  the  negative  has  been  dried,  soak  in  water  till 
wet,  then  cover  with  the  reducer,  and,  when  sufficiently  reduced, 
wash  and  refix  in  hypo.  It  is  well  adapted  for  local  reduction 
as  a  little  of  Solution  II.  may  be  applied  on  the  tip  of  the  finger. 
Cupric  Chloride.    Spiller  suggested  the  use  of — 

A. 

Alum      120  parts. 

Copper  sulphate       ...       ...        ..        ...    120  ,, 

Common  salt  ...       ...       ...       ...       ...    240  „ 

Water  1200  ,, 

B. 

Saturated  solution  of  salt. 

Before  use  mix  in  equal  parts  and  immerse  in  the  solution  till 
sufficiently  reduced,  then  wash  well. 

Cyanide  Reducers.  Several  formulae  have  been  suggested  for 
these,  but  their  action  is  not  to  be  depended  upon. 

Lainer's  Iodide  Reducer.  Lainer  has  suggested  the  follow- 
ing :  — 

Potassium  iodide    ...       ...      10  grains. 

Sodium  hyposulphite  . ..       ...       ...       ...  250 

Water   ...       ...       ...       ...       ...       ...       2\  ozs. 

in  which  the  negative  is  laid.  Reduction  takes  place  gradually 
and  evenly. 

To  Reduce  Prints.  Bromide  prints  may  be  reduced  in  exactly 
the  same  way  as  negatives.  Albumen ised  Paper  Prints  may  be 
reduced  by  dipping  into  cupric  chloride,  or  by  using  the  chloride 
of  lime  or  platinum  toning  baths.  To  Reduce  Ferro-Prussiate 
Prints,  dip  into  a  weak  bath  of  liq.  ammonia,  and  then  into 
weak  hydrochloric  acid. 

Reflected  Light  is  the  light  obtained  by  reflection  from  any 

381 


Ref] 


DICTIONARY  OF  PHOTOGRAPHY. 


mirror  or  white  surface.  It  is  extremely  useful  in  portraiture  for 
lighting  up  the  shadowed  side  of  a  sitter's  face ;  but  care  should 
be  taken,  however,  that  too  much  reflected  light  is  not  used,  or 
the  result  will  be  a  hard  and  lifeless  picture.  Mirrors  should 
rarely  be  used,  and  a  rough,  not  too  white  surface  is  the  best. 

Reflection  Of  Light.  When  a  ray  of  light  falls  upon  a 
mirror,  the  ray  is  bent  from  its  original  direction  into  another  ; 
this  is  said  to  be  reflection.  Reflection  of  light  obeys  certain 
well-known  laws,  the  first  of  which  is  that  the  reflected  ray  must 
lie  in  the  same  plane  as  the  incident  ray  ;  the  second  law  is  that 
the  angle  formed  by  the  reflected  ray  with  the  normal  must  be 
equal  to  the  angle  formed  by  the  incident  ray. 


C 

Fig.  82. 


The  reflected  ray,  ce,  is  in  the  same  plane  as  the  incident  ray, 
dc,  and  the  angle  ecf  is  equal  to  the  angle  dcf. 

Refraction  Of  Light.  When  a  ray  of  light  passes  obliquely 
from  one  transparent  medium  to  another  it  suffers  refraction, 
or  is  bent  out  of  its  course  on  emerging  from  that  medium.  Re- 
fraction obeys  well-known  laws  somewhat  similar  to  reflection. 
The  first  law  is  that  the  incident,  the  normal  and  the  refracted 
rays  are  in  the  same  plane,  and  the  second  that  the  angle  formed 
by  the  incident  ray  with  the  normal  bears  a  constant  ratio  to 
the  angle  formed  by  the  refracted  ray  with  the  normal.  By  con- 
stant ratio  is  meant  that  in  a  given  medium,  and  for  different 
angles  of  incidence,  the  ratio  of  the  refracted  to  the  incident  rays 
is  constant  when  light  passes  from  a  vacuum  into  the  substance ; 
practically,  it  means  that  the  same  substance  always  refracts 

382 


DICTIONARY  OF  PHOTOGRAPHY. 


[Res 


light  to  the  same  extent.  It  is  necessary  for  practical  opticians 
to  find  the  refractive  index  of  their  glass,  and  this  they  do  usually 
by  making  it  into  a  lens  of  known  surfaces,  and  finding  by  trial 
the  focus  of  the  lens.  It  can  be  done  more  scientifically  by 
decomposing  a  ray  of  white  light  by  means  of  a  prism  constructed 
of  the  glass,  and  measuring  the  refraction  of  a  certain  dark  line 
of  the  spectrum  by  suitable  instruments.  The  different  coloured 
rays  of  the  spectrum  have  different  refractive  indices,  that  for 
violet  being  the  greatest,  and  that  for  red  the  least ;  and  this  fact 
is  taken  into  consideration  in  the  achromatising  of  lenses.  (For 
further  information  on  Reflection  and  Refraction  the  reader  is 
referred  to  any  elementary  work  upon  light  or  optics.) 

Rembrandt  Portrait.  When  the  shaded  side  of  a  sitter  is 
portrayed  with  the  light  more  or  less  behind  the  head,  the  picture 
is  given  the  above  name,  from  a  fancied  resemblance  to  the  works 
of  that  great  master.    (See  Portraiture.) 

Removal  of  Film.  To  clean  the  films  off  old  and  useless 
negatives  nothing  is  better  than  soaking  the  negative  in  hot  water, 
and  then  rubbing  with  a  paste  composed  of  pumice-stone  powder 
and  glacial  acetic  acid. 

Residues.  The  saving  of  the  unused  silver  and  gold  salts 
in  use  in  photography  may  be  said  to  be  almost  beyond  the 
amateur,  unless  he  is  in  the  habit  of  doing  a  very  large  amount 
of  work,  but  the  following  directions  will  prove  useful : — To 
reduce  the  silver  from  the  fixing  baths,  the  old  solutions  should 
be  placed  in  a  tub  or  earthenware  vessel  with  some  sulphuretted 
potash  (liver  of  sulphur),  and  the  silver  will  be  precipitated  as 
a  black  deposit  of  sulphide,  Ag2S.  This  should  be  allowed  to 
collect  at  the  bottom  of  the  vessel  till  some  considerable  amount 
is  ready,  when  it  may  be  reduced  to  metallic  silver,  as  described 
below,  or  sent  to  the  refiner.  All  clippings  and  trimmings  from 
untoned  prints  should  be  reserved,  and  when  a  fair  quantity  is 
obtained  should  be  burnt,  commencing  at  the  top  of  the  pile,  or 
the  paper  may  be  beaten  to  pulp,  with  dilute  sulphuric  acid,  and 
strips  of  metallic  zinc  or  copper  placed  in  the  mixture;  metallic 
silver  will  be  precipitated,  and  the  zinc  or  copper  dissolved. 
The  washings  of  untoned  prints  should  be  placed  in  a  jar,  and 
common  salt  added  till  no  further  precipitate  is  caused,  and 
the  precipitate  may  be  collected  and  treated  as  above,  or  all  the 

383 


Res]  DICTIONARY  OF  PHOTOGRAPHY. 

residues  may  be  mixed  with  nitrate  of  potash  and  powdered 
charcoal,  and  fused  in  a  crucible.  To  reduce  old  toning  baths, 
whether  of  platinum  or  gold,  add  solution  of  ferrous  sulphate ; 
a  black  precipitate,  of  carbonate  and  oxide  of  iron  mixed  with 
metallic  gold,  results.  This  may  be  digested  in  aqua  regia,  and 
the  gold  in  the  resulting  solution  reprecipitated  by  ferrous  sul- 
phate in  a  pure  state,  when  it  can  be  redissolved  in  aqua  regia 
to  form  the  auric  chloride.  Ordinary  albumenised  paper  absorbs 
about  30  grs.  of  nitrate  of  silver,  equal  to  19  grs.  of  pure  silver 
for  every  sheet.  Each  sheet  weighs  about  340  grs. ;  therefore  a 
quire  will  weigh  about  8,160  grs.,  and  contain  about  456  grs.  of 
pure  silver.  Of  the  silver  used  in  sensitising  paper  will  be 
found — 

In  the  finished  print  about  ...       ...       3  per  cent. 

,,  cuttings  about      ...       ...       ...       7  „ 

„  washing,  before  toning,  about  50  to  55  „ 

„  fixing  bath   25  „  30 

,,  washing  after  fixing       ...       ...       5  ,, 

Restrainer.  Any  substance  used  to  prevent  the  too  energetic 
reducing  or  developing  action  of  any  chemical  upon  the  exposed 
film.  Restrainers  may  be  of  two  kinds — mechanical  and  chemi- 
cal. To  the  first  class  belongs  water  or  any  tanning  agent,  as 
chrome  alum,  which  renders  the  gelatine  less  permeable  to  the 
developer.  To  the  second  class  belong  any  soluble  bromide  or 
chloride,  and  the  citrates  of  potash,  soda,  and  ammonium.  A 
soluble  bromide  is  added  to  the  developer  to  check  the  reduction 
of  the  unaltered  silver  bromide,  the  soluble  bromide  seemingly 
forming  a  double  bromide  with  it,  which  is  less  acted  upon  by 
the  developer.  The  restraining  power  of  the  bromides  of  ammo- 
nium, potassium,  and  sodium  bear  the  following  proportion  to 
one  another : — Bromide  of  ammonium — 98  parts  are  equal  to 
119  parts  of  bromide  of  potassium,  and  equal  to  103  parts  of 
bromide  of  sodium.  Bromide  of  ammonium  is,  therefore,  the 
strongest,  potassium  bromide  the  weakest,  and  the  sodium  salt 
the  medium.  The  citrates  of  potassium,  sodium,  and  ammonium 
seem  to  act  in  entirely  a  different  manner ;  whereas  the  bromides 
prevent  the  excessive  deposit  on  the  high-lights  to  some  extent 
and  allow  detail  to  appear,  the  citrates  prevent  detail  and  allow 

384 


DICTIONARY  OF  PHOTOGRAPHY. 


[Res 


density  to  be  obtained.  To  make  these  restrainers,  the  bromides 
can  be  simply  dissolved  in  water,  as  follows  : — 

Ammonium  bromide    98  grs.    or  6  grms. 

Distilled  water,  to  make   980  mins.  ,,  60  c.cm. 

of  solution,  each  drachm  of  which  will  contain  6  grs.  of  bromide. 

Potassium  bromide    119  grs.    or   7  grms. 

Distilled  water,  to  make   980  mins.  ,,  60  c.cm. 

of  solution,  each  drachm  of  which  will  contain  Jf  grs.  of  bromide 
of  potassium,  equal  in  restraining  power  to  6  grs.  of  bromide  of 
ammonium. 

Sodium  bromide   103  grs.    or  6  grms. 

Distilled  water,  to  make   980  mins.  ,,  60  c.cm. 

of  solution,  each  drachm  of  which  will  contain  6£  grs.  of  sodium 
bromide,  equal  in  restraining  power  to  6  grs.  of  ammonium 
bromide,  or  to  7|  grs.  of  potassium  bromide. 

Citrate  of  Potash  Restrainer. 

Citric  acid  720   grs.  or  46  grms. 

Bicarbonate  of  potash    944  ,,  60  ,, 

or    Carbonate  of       „    884     „        57  ,, 

Distilled  water,  to  make   2h  ozs.  ,,  45  c.cm. 

of  solution. 

Citrate  of  Ammonium  Restrainer. 

Citric  acid   720  grs.    or  46  grms. 

Liq.  ammonia,  *88o        ...       ...    630   mins.  „  38  c.cm. 

Distilled  water,  to  make   2\  ozs.        45  ,, 

of  solution. 

Citrate  of  Soda  Restrainer. 

Citric  acid   720  grs.  or  46  grms. 

Bicarbonate  of  soda    884     ,,        57  ,, 

or    Carbonate  of  soda  (crystallised)    1,440     „    ,,  93  ,, 
Distilled  water,  to  make   2$-  ozs.  ,,  45  c.cm. 

of  solution.  These  solutions  will  keep  indefinitely,  and  may  be 
diluted  as  wanted  by  adding  one  part  of  the  above  to  5  parts  of 
water.    The  advantage  of  these  last  three  restrainers  is  that 

385  CC 


Ret] 


DICTIONARY  OF  PHOTOGRAPHY. 


when  a  negative  shows  plenty  of  detail,  but  refuses  to  gain 
density,  the  addition  of  a  little  of  one  of  the  dilute  solutions 
may  be  made,  and  the  plate  left  for  hours  if  necessary,  till  the 
required  density  is  obtained,  without  the  slightest  sign  of  fog. 

Retouching  is  the  operation  of  doctoring  a  negative  by  aid  of 
a  pencil  or  by  use  of  a  brush  and  colour,  so  as  to  hide  the  defects 
of  manipulation  or  soften  down  the  otherwise  too  obtrusive 
freckle  or  wrinkle  in  a  sitter's  face.  The  subject  is  too  compre- 
hensive to  enter  upon  at  any  length,  as  the  necessary  qualifica- 
tions for  a  good  retoucher  for  the  face  and  hands,  which  are 
generally  those  parts  which  it  is  desired  to  retouch,  are,  first,  a 
general  idea  of  the  anatomical  position  of  the  muscles  and  bones 
of  the  hands  ;  and,  secondly,  considerable  artistic  skill  in  wielding 


Fig,  3- 

the  pencil  or  brush.  But  for  the  operator  who  may  desire  to 
retouch  a  landscape  negative,  so  as  to  be  able  to  block  out  any 
pinhole  in  the  sky  or  other  light  portion,  the  following  may  be 
of  some  assistance : — Some  sort  of  retouching  desk  is  needed, 
and  this  can  be  improvised  from  material  within  the  reach  of 
every  one,  all  that  is  necessary  being  a  printing-frame  of  the 
correct  size,  a  deal  board,  a  piece  of  black  cardboard,  and  a 
small  mirror  or  white  card.  Unscrew  the  springs  of  the  printing- 
frame  and  temporarily  remove  them  altogether,  make  a  small 
hole  in  one  end  of  the  face  of  the  frame,  have  a  deal  board 
about  12  ins.  long  and  6  ins.  broad,  and  arrange  as  shown  in 
diagram  : — D d,  deal  board;  ss,  two  nails  driven  well  into  board 
to  prevent  frame  slipping ;  p,  the  support  for  frame ;  and  b,  the 
black  card  to  prevent  top  light.  A  mirror  or  white  card  is  laid 
upon  dd  underneath  the  frame  F,  so  as  to  reflect  the  light  up 

386 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ret 


through  the  negative  lying  in  the  rebate  of  the  frame.  If  the 
reflection  from  the  mirror  be  too  great,  a  piece  of  ground-glass 
or  a  focussing  screen  may  be  intervened  midway  between  frame 
and  mirror,  in  the  position  of  the  dotted  line.  The  negative  to 
be  retouched  should  be  varnished  well  with  any  good  negative 
varnish,  and  allowed  to  dry  thoroughly ;  then  on  those  places 
where  retouching  is  required  should  be  dusted  a  little  very  finely 
powdered  cuttle-fish,  and,  using  the  finger  as  a  pad,  rub  the 
powder  up  and  down  or  in  a  circular  manner,  till  on  examining 
the  film  through  a  magnifying  glass  it  is  seen  to  be  quite  rough 
now  dust  the  superfluous  powder  off,  and  it  is  ready  for  work. 
The  amateur  retoucher  had  better  begin  by  using  lead  pencil,  a 
Faber's  or  Hardtmuth's  HHHH  or  HflHHHH  being  perhaps 
the  most  suitable,  and  the  point  should  be  sharpened  in  the 
following  manner: — The  pencil  point  should  always  be  kept 


very  sharp  by  rubbing  on  fine  emery  paper.  Now  touch  the 
abraded  surface  over  the  pinhole  in  a  circular  manner  till  the 
hole  is  no  longer  visible.  It  is  as  well  after  several  pinholes 
have  been  retouched  to  take  a  print  from  the  same  to  see 
whether  they  show  or  not.  Instead  of  the  cuttle-fish  advised 
above,  any  of  the  following  matt  varnishes  may  be  used  : — 

Amber  resin    10  grs.  or    I  grm. 

Benzole    I  oz.   „  50  c.cm. 

Dissolve,  and  allow  to  subside  for  twenty-four  hours  before  use. 
Gum  dammar      ...        ...        ...    10  grs.     or    1  grm. 

Canada  balsam    ...       ...       ...      5    ,,       ,,  0  5  ,, 

Turpentine    1  oz.      ,.50  c.cm. 


Shellac    36    „       ,,  2  grms. 

Mastic    36   ,,  2  ,, 

Ether    12  drms.  ,,  45  c.cm. 

Dissolve,  and  add 


Or 


Sandarac 


6  grs. 


„  0-4  grm. 


Benzole 


2  drms.  or    7  c.cm. 


3*7 


Rev] 


DICTIONARY  OF  PHOTOGRAPHY. 


Reversal  is  when  those  parts  of  the  image  which  should 
appear  dark  in  the  negative  come  up  light,  and  vice  versa. 
It  is  due  to  the  extreme  action  of  light,  and  is  also  known 
as  solarisation.  There  is  no  remedy  when  such  has  been 
effected. 

Reversed  Negatives.  This  means  that  the  position  of  the 
picture  is  reversed  as  regards  right  and  left.  Reversed  negatives 
are  an  absolute  necessity  for  photo-mechanical  work.  They 
may  be  made  in  the  following  different  ways : — First,  in  the 
camera  direct;  secondly,  by  reversing  the  negative  film  itself; 
thirdly,  by  reproduction  from  other  negatives.  First  method  : 
Taken  in  the  camera  direct.  This  again  may  be  divided  into 
three  heads — viz.,  (a)  those  taken  by  means  of  a  silvered  re- 
flector ;  (b)  those  taken  by  means  of  a  prism  ;  and  (c)  those  taken 
through  the  glass  plate  on  the  back  of  the  film.  By  the  first  of 
these  methods  a  piece  of  glass  or  metal  silvered  on  the  external 
surface  must  be  used,  and  mounted  in  the  following  manner: — 


c,  camera  ;  l,  lens ;  f  a  b  d  is  the  section  of  a  hood  which  can 
be  screwed  on  to  a  camera ;  a  d,  the  reversing  mirror,  placed  at 
an  angle  of  450  with  the  lens,  and  so  adjusted  that  the  axis  of 
the  lens  is  continued  to  the  centre  of  the  mirror ;  e  is  a  small 
door,  which  can  be  opened  or  closed  at  will.  The  camera  is 
placed  sideways  towards  the  object,  which  is  reflected  from  the 
exterior  surface  of  a  d  to  the  lens.  By  the  second  method  a 
right-angled  prism  is  used,  as  shown  in  the  diagram.  The 
principle  involved  being  precisely  the  same  as  with  the  mirror, 
the  camera  is  again  turned  sideways  to  object,  a  b  is  a  hood  to 
fit  on  lens  to  take  the  place  of  the  cap.  c  c  is  a  right-angled 
prism,  whose  breadth  is  greater  than  the  diameter  of  the  front 


Fig.  85. 


388 


DICTIONARY  OF  PHOTOGRAPHY. 


[Rev 


glass  of  lens.  All  the  surfaces  except  c  c  are  enclosed  in  brass- 
mounting,  but  the  surface  H,  opposite  to  the  right  angle,  must 
not  touch  the  glass.  E  is  a  shutter  for  exposing  ;  F  F,  the  screws 
for  clamping  same.  The  third  method  is  by  taking  negatives 
through  the  glass.  The  most  convenient  way  of  doing  this  is  to 
have  a  piece  of  glass  of  the  same  thickness  as  used  for  the  plate 
ground  on  one  side,  and  the  ground  surface  placed  outside,  just 
the  opposite  way  to  the  usual  focussing  screen.  The  back  of 
the  plate  must  be  carefully  cleaned,  and  should  be  inserted  in  the 
dark  slide,  with  the  glass  towards  the  shutter  of  slide.  Care 
must  be  taken  that  the  spring  used  to  keep  the  plate  in  position 
does  not  injure  the  film. 


a 


Fig.  86. 


Second  method  of  procedure  :  By  reversing  the  negative  film 
itself.  This  is  comparatively  easy,  and  can  be  done  as  follows  : — 
The  negative  is  taken  and  developed  in  the  ordinary  way. 
washed  and  dried,  and  is  coated  with  a  solution  of  india-rubber 
in  benzole,  and  when  dry  coated  with  transfer  collodion  made  as 
follows  : — 

Pyroxyline    24  grs.    or    I  5  grms. 

Castor  oil  24  mins.  ,,     15  c.cm. 

Methylated  spirit,  '805  ...       ...      2  ozs.     „  60  ,, 

,,        ether,  730   1  oz.  ,,25 

And  allowed  to  dry,  and  placed  in  a  bath  of 

Hydrofluoric  acid    1  drm.  or     4  c.c.m. 

Distilled  water   10  ozs.   ,,250  ,, 

339 


Risj 


DICTIONARY  OF  PHOTOGRAPHY. 


The  film  will  soon  begin  to  get  loose,  and  should  be  gently 
raised  up  and  floated  off  into  a  bath  of  clean  water  and  washed 
thoroughly,  and  then  floated  in  a  reverse  position — that  is,  with 
the  collodionised  side  downwards — on  to  a  plate  coated  with  a 
warm  solution  of  gelatine  (about  5  grs.  to  the  ounce).  It  should 
be  then  squeegeed  into  contact  and  left  to  dry. 

The  third  method :  By  reproduction  from  the  negative.  Mr. 
Bolas  proposes  the  following  plan  : — A  dry  plate  is  soaked  for  five 
minutes  in  a  4  per  cent,  solution  of  bichromate  of  potash,  rinsed 
once  or  twice  in  water,  and  then  dipped  into  a  bath  of  equal 
parts  of  methylated  spirit  and  water,  the  superfluous  moisture 
blotted  off,  and  dried.  All  these  operations  must  be  conducted 
in  the  dark-room.  It  is  then  exposed  under  the  negative  to  be 
reversed  to  sunlight  for  three  or  four  minutes,  when  a  faint 
delicate  image  will  be  seen  impressed  ;  it  is  then  washed  and 
developed  with  ferrous  oxalate  or  alkaline  pyro,  and  fixed  and 
washed  as  usual.    The  result  is  a  reversed  and  negative  image. 

Rising  Front.  A  movable  piece  of  wood  fitted  to  the  front 
of  camera,  which  can  be  moved  up  and  down  so  as  to  exclude  or 
include  more  or  less  of  the  foreground  of  a  picture  without  shift- 
ing camera.  It  should  be  sparingly  used,  however,  as  of  course 
the  shifting  of  the  lens  either  up  or  down  causes  the  optical  axis 
of  the  lens  to  be  altered  with  regard  to  the  centre  of  the  plate ; 
and  as  the  brightest  illumination  is  obtained  with  the  central 
rays  it  is  obvious  that  unequal  illumination  may  ensue. 

Rives  Paper.  A  particular  make  of  paper  specially  prepared 
for  photographic  purposes. 

Roller  Slide.  The  introduction  of  films  and  paper  supports 
for  the  sensitive  emulsion  suggested,  of  course,  the  natural  idea 
of  using  the  same  in  a  continuous  band  for  the  purpose  of 
exposing  on  many  subjects  without  changing,  and  for  this  purpose 
the  roller  slide  has  been  introduced. 

Rolling  Prints.  Consists  of  passing  prints  between  two 
rollers,  or  between  a  roller  and  a  bed  of  steel.  It  improves  the 
appearance,  and  causes  the  print  to  lie  flat. 

Ruby  Light.    See  Dark-Room. 

Salicylic  Acid  (Ger.,  Salicylsaure ;  Fr.,  Aade  Salicylique). 
39° 


DICTIONARY  OF  PHOTOGRAPHY. 


[Shu 


HC7H.-03  =  138.  Occurs  naturally,  but  is  prepared  commercially 
by  heating  carbolic  acid  with  caustic  soda  and  passing  carbonic 
acid  into  the  mixture.  Solubility  :  1  in  700  of  cold  water,  1  in  9 
of  boiling  water,  1  in  4  of  alcohol  ;  20  grs.  with  20  grs.  of  borax 
or  acetate  of  potash  will  dissolve  in  1  oz.  of  water.  It  is  but 
rarely  used  in  photography  ;  as  a  preservative  it  is  added  to  some 
mountants,  and  as  salicylate  of  soda  is  recommended  to  give 
increased  sensitiveness  to  dry  plates. 

Shutters,  Instantaneous.  When  the  images  of  rapidly 
moving  objects  are  desired,  it  is  found  that  the  hand  is  not  quick 
enough  to  uncover  and  recap  the  lens,  therefore  some  mechanical 
device  is  used  for  this  purpose,  and  is  called  an  instantaneous 
shutter.  The  names,  styles,  and  prices  of  these  are  legion,  but 
they  may  be  conveniently  divided  into  two  main  classes :  (I.) 
Exposing  Shutters ;  (II.)  Rapid  Shutters.  As  some  practical 
guide,  the  following  notes  on  each  form  are  given : — 

(I.)  Exposing  Shutters.  These  are  more  or  less  simple 
arrangements  devised  to  replace  the  cap,  and  are  usually  fitted 


Fig.  87. 


to  the  lens  hood  and  actuated  by  a  pneumatic  ball  and  tube, 
which  releases  that  portion  of  the  shutter  covering  the  lens,  and 
again  covers  the  objective  when  the  necessary  exposure  has  been 
given.  Usually  pressure  on  a  ball,  or  the  tension  on  a  string  or 
cord,  raises  a  flap  from  in  front  of  the  lens,  which  remains  raised 
till  such  pressure  or  tension  is  removed  when  the  necessary  ex- 
posure has  been  given.  Many  of  the  shutters  classed  in  Sec- 
tion II.  are  arranged  to  give  time  exposure  also. 

(II.)  Rapid  Shutters.  This  class  may  be  again  conveniently 
divided  into  (a)  shutters  working  in  front  of  the  lens,  (b)  those 

391 


ShuJ 


DICTIONARY  OF  PHOTOGRAPHY. 


working  behind  the  lens,  (c) 


be  elongated  or  shortened  by 


those  working  in  the  diaphragm 
slot,  (d)  those  working  in  front 
of  the  sensitive  plate. 

(a)  Shutters  Working  in  Front 
of  the  Lens.  I  have  to  confess 
that  the  treatment  of  this  subject 
is  like  an  eternal  division  sum, 
but  my  idea  is  to  provide  a 
practical  guide  to  the  choice  of 
a  shutter.  We  may  again  divide 
into  classes — 

(Class  II.,  a  i)  The  Simple 
Drop.  This  consists  of  a  sliding 
piece  of  wood  or  ebonite,  with 
an  aperture  which,  passing  in 
front  of  the  lens,  makes  the  ex- 
posure. The  longer  the  aperture 
in  the  dropping  piece  the  more 
even  the  illumination  of  the  plate. 
From  theoretical  considerations 
the  aperture  should  take  the  form 
shown  in  the  accompanying  dia- 
gram (fig.  87),  the  distance  along 
the  dotted  line  a  b  being  made 
equal  to,  or  twice,  or  thrice,  the 
diameter  of  the  lens :  the  narrower 
this  aperture  the  quicker  the  ex- 
posure, but  the  less  light  admitted 
during  exposure.  The  longer  the 
slide  drops  before  uncovering  the 
lens,  the  more  even  the  illumin- 
ation of  the  plate  and  the  shorter 
the  exposure.  In  this,  as  in  all 
shutters  fitting  on  the  hood  of  the 
lens,  the  aperture  of  the  shutter 
should  never  be  smaller  than  the 
lens  aperture,  or  it  acts  as  a  stop. 
Some  of  the  drop-shutters  are  so 
arranged  that  the  aperture  may 
1  additional  sliding  piece. 
92 


DICTIONARY  OF  PHOTOGRAPHY. 


[Shu 


(CI.  II.,  a  2)  The  Flap  and  Drop.  This  is  a  combination  of 
the  flap  with  a  drop,  and  the  flap  is 
raised,  and  then  at  a  given  point  the 
drop  falls.  This  class  of  shutter 
gives  more  exposure  to  the  fore- 
ground than  the  sky.  A  modification 
of  this  form  has  been  introduced,  in 
which  the  flap  rises,  and  then  turns 
on  a  bar  and  falls  like  a  drop. 

(CI.  II.,  a  3)  The  Double  Drop. 
In  this  form  a  sliding  piece  is  raised 
by  pulling  a  string,  and  then  when 
the  lens  is  completely  uncovered 
another  sliding  piece  falls,  closing 
the  aperture  ;  thus  more  exposure 
is  given  to  the  foreground  than  sky. 

(CI.  II.,  a  4)  The  Rotating  Screen. 
In  this  style  of  shutter  a  rotating 
screen  uncovers  and  covers  the  lens 
aperture.  In  several  shutters  of  this 
class  a  special  shape  is  given  to  the 
rotating  screen  to  give  more  exposure 
to  the  foreground. 

(CI.  II.,  a  5)  The  Flap  and  Double 
Flap.  The  principle  of  this  class 
consists  of  a  flap  which  is  raised 
and  lowered,  or  one  which  is  raised, 
opening  the  lens,  and  another  closing 
the  lens; 

(CI.  II.,  a  6)  The  Go  and  Return. 
The  disadvantage  of  this  class  of 
shutter  is  that,  if  the  moving  part 
is  heavy  and  not  counterbalanced, 
the  reversal  of  the  motion  at  the 
critical  moment  of  exposure,  that  is, 
when  the  lens  is  fully  open,  is  apt 
to  cause  vibration  and  blurring  of 
the  outline.    Many  shutters  of  this 

class  are  constructed  to  fit  in  front  of,  behind,  or  between,  the 
lenses. 

393 


DICTIONARY  OF  PHOTOGRAPHY. 


(CI.  II.,  a  7)  The  Blind  Pattern. 
This  is  again  a  very  favourite  form, 
and  one  which,  acting  on  the  prin- 
ciple of  the  simple  drop-shutter, 
gives  a  fair  range  of  speed.  It 
consists  of  a  blind  of  opaque 
cloth  fastened  at  each  end  to 
rollers,  the  lower  one  being  pro- 
vided with  a  coiled  spring,  the 
upper  with  a  small  milled  head 
for  winding  up  the  material,  which, 
on  the  release  of  a  catch,  passes 
in  front  of  the  lens,  exposing  the 
plate  and  again  covering  the  lens. 

(CI.  II.,  a  8)  Shutters  opening 
from  Centre.  The  form  of  opening 
takes  various  shapes,  from  the  long 
straight  narrow  strip — the  eyelid, 
and  the  diamond.  The  first  form 
of  opening  is  given  by  two  roller 
blinds  opening  from  the  centre 
and  closing  again  to  the  centre. 
In  the  second  form,  the  aperture 
takes  first  the  shape  of  an  eyelid, 
and  opening  from,  and  closing  to, 
the  centre.  In  the  third  form 
the  aperture  takes  the  form  of  a 
diamond,  opening  from,  and  closing 
to,  the  centre. 

(CI.  II.,  a  9)  The  Ever-Set 
Shutter.  This  shutter  is  of  French 
origin,  but  is  now  made  by  many 
English  firms. 

(CI.  II.,  b)  Shutters  Working 
behind  the  Lens.  There  are  few 
shutters  on  the  market  specially 
constructed  to  work  in  this  position, 
though  many  of  those  working  in 
front  of  the  lens  can  be  thus  used, 
especially  the  blind  pattern. 

394 


DICTIONARY  OF  PHOTOGRAPHY. 


[Shu 


(CI.  II.,  c)  Shutters  Working  Between  the  Lenses.  This 
variety  is  again  divided  into  (i)  The  go  and  return  ;  (2)  the 
blind  or  drop  ;  (3)  opening  from  and 
closing  to  centre  with  eyelid  aperture; 
(4)  opening  from  and  closing  to  centre 
with  diamond  aperture ;  (5)  opening 
from  and  closing  to  centre  with  longi- 
tudinal strip  opening;  (6)  Iris  dia- 
phragm action  :  (7)  rotating  screen. 

(CI.  II.,  c  1)  The  Go  and  Return. 
This  form  has  for  some  time  held  the 
front  rank  in  between-lens  shutters,  but 
is  open  to  the  theoretical  objection  that 
the  reversal  of  the  motion  at  the  critical 
moment  of  exposure,  when  the  lens 
is  fully  open,  is  liable  to  cause 
vibration. 

(CI.  II.,  c  2)  The  Blind  or  Drop.  In 
the  case  of  the  drop  it  is  obvious  that 
the  lens  mount  has  to  be  cut  to  allow 
the  dropping-piece  to  pass  through. 
This  has,  probably  for  this  reason,  found 
but  little  favour.  The  blind  form  is 
practically  the  same  as  that  made  for 
the  front  of  the  lens  but  with  a  narrow 
slit 

(CI.  II.,  c  3)  Opening  from  and 
Closing  to  the  Centre  with  Eyelid 
Aperture.  This  form  of  aperture  is  a 
favourite  one. 

(CI.  II.,  c  4)  Opening  from  and 
Closing  to  the  Centre  with  Diamond 
Aperture. 

(CI.  II.,  c  5)  Opening  fro?n  and 
Closing  to  the  Centre  with  Longitudinal 
Strip  Opening.  So  far  as  I  am  aware 
there  is  only  one  commercial  shutter 
which  gives  this  form  of  opening,  and 
it  consists  of  double  blinds  which  work  in  opposite  directions. 

(CI.  II.,  c  6)  Opening  from  and  Closing  to  the  Centre  with 

395 


DICTIONARY  OF  PHOTOGRAPHY. 


Iris  Diaphragm  Action.  Sever  a 
new  shutters  have  lately  been 
introduced  of  this  pattern. 

(CI.  II.,  £"7)  Rotating  Screen. 
In  this  form  a  screen  pierced 
with  a  circular  aperture  rotates 
across  between  the  lenses. 

(CI.  II.,  d)  Shutters  Worki?ig 
in  front  of  the  Sensitive  Surface. 
— In  this  form  of  shutter,  which 
is  by  no  means  new,  a  roller 
blind  with  a  narrow  slit  in  it, 
passes  immediately  in  front  of 
the  sensitive  surface,  thus  ex- 
posing the  same  in  successive 
portions,  and  allowing  the  lens 
to  act  with  full  aperture  for  the 
whole  period  of  exposure— no 
matter  how  short  that  exposure 
be.  This  shutter  also  possesses 
the  advantage  of  allowing  any 
focus  lens,  or  a  lens  of  any 
diameter,  being  used  without  any 
difficulty. 

As  to  make  a  choice  of  shutters 
it  is  necessary  to  understand 
something  of  the  manner  in 
which  they  act,  we  will  first  of 
all  show  the  lens  working  at  full 
aperture  fig.  88.  From  this  it  will 
be  seen  that  far  more  light  is 
transmitted  axially,  that  is,  with 
the  horizon  rays,  than  with  the 
sky  and  foreground,  but  if  he  lens 
is  stopped  down  tofji6  as  shown 
in  fig,  89  the  illumination  is  pract- 
ically equal.  For  this  particular 
portion  of  my  notes  shutters 
are  only  divided  into  four  main 
classes  : — a,  those  acting  in  front 
396 


DICTIONARY  OF  PHOTOf 


of  the  lens  ;  b,  in  between  the   

lenses  ;  c,  behind  the  lens  ; 
and  d,  in  front  of  the  plate. 
To  learn  the  action  of  any 
shutter  on  the  light  and  image 
transmitted  by  a  lens,  the 
reader  is  advised  to  take  a 
piece  of  card,  and  pass  it 
across  the  diagram  in  the 
direction  of  the  moving  parts 
of  the  actual  shutter  ;  he  will 
thus  be  able  to  see  the  action 
of  shutter  he  is  thinking  of 
buying.  As  an  example,  we 
will  take  the  Go  and  Rehcm 
shutter  acting  in  front  of  the 
lens,  and  show  it  when  the 
moving  piece  is  halfway  up 
fig.  90.  From  this  it  will  be 
seen  that  there  is  considerable 
difference  in  the  amount  of 
light  received  by  the  plate. 
It  is  not  a  matter  of  in- 
difference whether  the  shutter 
be  close  to  the  lens  or  not, 
as  will  be  seen  from  fig.  91 
there  being  a  considerable 
gain  when  it  is  close  to  the 
lens.  With  shutters  open- 
ing from,  and  closing  to, 
the  centre  in  front  of  the 
lens,  the  centre  of  the 
picture,  which  is  generally  I 
the  horizon  of  the  picture  / 
receives  far  more  light  than 
the  margins,  which  include  , 
the  sky  and  foreground,  the 
action  of  such  a  shutter  being 
shown  in  fig.  92.  When  this  / 
class  of  shutter  acts  between  ' 


397 


Sil] 


DICTIONARY  OF  PHOTOGRAPHY. 


the  lenses  it  is  in  the  very  best  position,  and  acts  for  part  of  the 
time  as  a  small  stop,  and  therefore  should  give  better  definition 
with  a  large  aperture  than  any  other  kind.  The  last  type  of 
shutter  is  the  focal  plane,  and  this  is  a  flexible  blind  working 
close  to  the  surface  of  the  plate.  This  is  the  best  position  for 
a  shutter,  as,  no  matter  how  brief  the  exposure,  the  whole  of 
the  light  transmitted  by  the  lens  reaches  the\plate.  The  action 
of  such  a  shutter  is  shown  in  fig.  93. 

As  a  practical  help  also  I  have  added  a  table  giving  the  speeds 
of  various  commercial  forms  of  shutters  arranged  in  classes 
as  above  (See  Appendix). 

Silver  (Ger.,  Silber;  Fr.,  Argent;  Ital.,  Argentd).  Ag=  108. 
This  metal  occurs  either  alone  or  in  combination  with  various 
metals  and  elements.  There  are  three  principle  methods  of 
extraction  of  the  metal  from  its  ores  :  (a)  alloying  with  lead, 
and  subsequent  cupellation,  (#)  amalgamation  with  mercury,  and 
recovery  of  mercury  by  distillation,  (V)  hydrometallurgic  process, 
in  which  the  silver  is  converted  into  a  soluble  salt,  and  pre- 
cipitated with  copper.  Silver  may  be  obtained,  chemically  pure, 
by  decomposing  the  chloride  AgCl  with  hydrochloric  acid  and 
zinc ;  the  metal  separates  in  a  spongy  form,  and  may  be  fused 
under  carbonate  of  soda  to  prevent  access  of  air,  and  obtain  a 
button  of  silver  ;  or  by  adding  hydrochloric  acid  to  silver  nitrate 
solution,  collecting  the  chloride  and  reducing  this  to  the  metallic 
state.  When  pure,  silver  will  absorb  twenty-two  times  its 
volume  of  oxygen  if  exposed  to  the  air  in  a  melted  state, 
but  on  cooling  the  oxygen  is  given  off.  It  is  the  best  conductor 
of  heat  and  electricity  of  all  the  metals,  and  it  is  extremely 
malleable  and  ductile.  It  can  be  hammered  into  sheets  1 0  fa 0  0  of 
an  inch  in  thickness.  When  examined  by  transmitted  light  at 
this  stage,  it  is  of  a  distinct  emerald  green  colour.  It  can  be 
drawn  into  wire,  400  ft.  of  which  only  weigh  1  gr.,  and  its 
tenacity  is  so  great  that  a  silver  wire  ^  of  an  inch  in  diameter 
will  support  a  weight  of  187  lbs.  It  melts  at  about  1,832°  F. 
Molten  caustic  alkalies,  or  alkaline  nitrates,  have  no  effect  upon 
it ;  it  is  unaffected  by  the  air,  but  oxidised  by  ozone  ;  sulphurous 
vapours,  however,  immediately  act  upon  it,  forming  sulphides. 
Many  silver  salts  are  acted  upon  by  light,  with  partial  reduction 
to  the  metallic  state.    Silver  is  soluble  in  nitric  acid  and  boiling 

398 


DICTIONARY  OF  PHOTOGRAPHY. 


[Sil 


sulphuric  acid,  and  only  partially  so  in  hydrochloric  acid.  The 
standard  British  coinage  contains  92*5  parts  of  pure  silver  and 
7-5  parts  of  copper.  In  the  United  States  and  France  10  per 
cent,  of  copper  is  used,  and  in  Germany  25  per  cent.  To  pre- 
pare pure  silver  from  any  coin,  the  following  process  will  be 
found  efficient : — Place  the  coin  either  entire,  or  preferably  cut 
up  small,  in  a  test  tube,  with  one  part  of  pure  nitric  acid,  and 
two  parts  of  water;  apply  a  gentle  heat,  and  an  action  com- 
mences at  once,  orange-red  fumes  of  nitric  oxide  being  evolved ; 
if  after  the  lapse  of  some  time  the  whole  of  the  coin  is  not 
dissolved,  add  more  nitric  acid,  and  again  apply  heat.  When  the 
coin  is  dissolved,  the  solution  will  be  seen  to  be  of  a  bright  blue 
colour,  due  to  the  copper ;  pure  silver  can  be  obtained  from  this 
solution  by  evaporating  to  dryness,  and  fusing  strongly  the 
resulting  mass.  A  little  taken  out  and  dissolved  in  water  should 
give  no  blue  coloration  with  solution  of  ammonia  ;  or  sheet 
copper  may  be  placed  in  the  acid  solution,  when  a  precipitate 
of  pure  silver  will  take  place,  which  may  be  collected  and  again 
dissolved  in  nitric  acid  to  form  solution  of  nitrate  of  silver;  or 
the  precipitate  may  be  collected  and  fused  as  above  to  obtain  a 
button  of  silver. 

Silver  Acetate  (Ger.,  Silberacetat,  Essigsdures  Silberoxyd). 
AgC2H302  =  167.  Is  obtained  in  white  crystals  by  mixing 
silver  nitrate  with  a  soluble  acetate.  The  crystals  are  soluble, 
1  in  100  parts  of  water. 

Silver  Albuminate  (Ger.,  Silber  Albuminat ;  Fr.,  Albuminate 
d1  Argent;  Ital.,  Albuminate  d'Argento).  The  white  precipitate 
obtained  by  adding  nitrate  of  silver  in  solution  to  albumen  in  the 
dark  is  thus  termed.  It  is  a  complex  compound  of  oxide  of 
silver  and  albumen,  and  is  reduced  to  a  red  sub-compound  by 
the  action  of  light.  It  is  this  reaction  which  occurs  when  printing 
on  sensitised  albumenised  paper. 

Silver,  Ammonio-Nitrate  of  (Ger.,  Salpetersdurcs  Si  I  be  r- 
oxyd-a?n?noniak;  Fr.,  Nitrate ammoniacald' argent).  2  NH3AgN03. 
The  pure  salt  can  be  obtained  by  exposing  powdered  nitrate  of 
silver  to  ammonia  gas,  combination  taking  place  very  rapidly, 
and  with  evolution  of  sufficient  heat  to  fuse  the  resulting  com- 
pound, which  contains  22-5  per  cent,  of  ammonia,  NH;{,  and  77-5 

399 


Sil] 


DICTIONARY  OF  PHOTOGRAPHY. 


per  cent,  of  silver  nitrate,  AgNOr  Ammonio-nitrate  of  silver  is 
used  for  sensitising  plain  salted  paper.  It  cannot  be  used  for 
the  same  purpose  for  albumenised  paper,  as  the  albumen  would 
be  dissolved  ;  it  is  also  used  in  making  emulsions.  It  may  also 
be  prepared  by  dissolving  silver  oxide  in  solution  of  ammonium- 
nitrate,  or  adding  ammonia  drop  by  drop  to  solution  of  silver 
nitrate  till  the  precipitate  first  formed  is  redissolved.  A  solution 
containing  less  ammonia  may  be  obtained  by  dividing  the  solu- 
tion of  silver  nitrate  into  two  equal  parts,  to  the  one  adding 
sufficient  ammonia  to  obtain  a  clear  solution,  and  then  adding 
the  other  half  of  the  silver  nitrate  solution. 

Silver  Bromide  (Ger.,  Bromsilber ;  Fr.,  Bromure  d' argent ; 
Ital.,  Bromuro  d" argento).  AgBr  =  188.  Can  be  prepared  by 
direct  union  between  the  elements,  as  in  the  Daguerrotype 
process,  or  by  double  decomposition  between  nitrate  of  silver 
and  any  soluble  bromide,  as  in  dry-plate  processes : — 

AgN03  +       KBr       =     AgBr     +  KN03 
Silver  Potassium  _     Silver  Potassium 

nitrate  bromide    ~~   bromide  nitrate. 

Or  it  may  be  prepared  by  dissolving  carbonate  or  oxide  of 
silver  in  hydrobromic  acid.  Bromide  of  silver  is  darkened  to 
a  tawny  grey  by  the  prolonged  action  of  light,  with  evolution  of 
bromine ;  but  by  short  exposures,  as  in  the  camera,  it  is  said  to 
be  reduced  to  a  sub-bromide,  or,  as  Carey  Lea  calls  it,  a  photo- 
bromide  of  silver.  Sub-bromide  of  silver  in  this  stage  is  pre- 
cisely the  same  in  physical  appearance  as  the  bromide ;  but  it 
is  more  easily  reducible  by  certain  salts,  which  constitutes  the 
process  of  Development  (g.v.).  Bromide  of  silver  is  practically 
insoluble  in  water,  alcohol,  and  ether,  but  soluble  in  solution 
of  alkaline  hyposulphites,  cyanides,  sulpho-cyanides,  ammonia 
(about  i  :  iooo),  and  saturated  solutions  of  most  chlorides, 
bromides,  and  iodides.  Silver  bromide  is  the  usual  sensitive  salt 
in  emulsions,  either  alone  or  combined  with  iodide  and  chloride. 

Silver  Carbonate  (Ger.,  Silbercarbonat,  Kohlensdures  Silber; 
Fr.,  Carbonate  d'a?gent;  Ital.,  Carbanato  d'argento)  Ag2C03  = 
276.  This  can  be  obtained  as  a  yellowish  precipitate  by  mixing 
silver  nitrate  and  sodium  carbonate  solutions.  It  blackens  in 
light,  and  is  partly  decomposed  by  boiling  with  water  into  oxide. 

400 


DICTIONARY  OF  PHOTOGRAPHY. 


[Sil 


It  is  insoluble  in  water,  alcohol,  and  ether,  but  is  soluble  in  all 
the  solvents  of  the  haloid  salts  of  silver.  It  has  been  used  in 
emulsion  making,  either  for  forming  bromide,  by  solution  in 
hydrobromic  acid,  or  in  the  form  of  ammonio-carbonate  of  silver,  by 
dissolving  the  carbonate  in  ammonia.  It  has  also  been  suggested 
by  Burton  and  others  for  gelatino-chloride  printing-out  papers. 

Silver  Chloride  (Ger.,  Chlorsllber,  Silberchlorid ;  Fr.,  Chlorure 
d'arge?it;  Ital.,  Chloruro  d'argentd).  AgCl  =  143*5.  Can  be 
obtained  by  direct  union  between  the  elements,  or  by  double 
decomposition  with  nitrate  of  silver  with  a  soluble  chloride, 

AgN03  +  NaCl  =  AgCl  +  NaN03 ; 

or  by  adding  hydrochloric  acid  to  silver  nitrate, 

AgN03  +  HC1  -  AgCl  +  HNO3. 

It  also  occurs  as  a  native  ore,  called  horn  silver,  from  its  general 
appearance.  On  exposure  to  light  when  absolutely  pure  or  dry 
no  change  takes  place ;  but  with  the  smallest  trace  of  organic 
matter  or  water  it  passes  from  white  through  varying  shades  of 
purple  to  black,  chlorine  being  disengaged,  and  a  complex  body, 
now  definitely  stated  to  be  a  mixture  of  chloride  (AgCl),  oxy- 
chloride  (AgCIO),  and  metallic  silver  (Ag)  resulting.  It  melts 
at  about  2600  F.,  and  is  not  decomposed  when  heated  with 
carbon,  but  is  immediately  reduced  by  heating  in  a  current  of 
nascent  hydrogen.  Zinc,  iron,  and  copper  reduce  the  chloride, 
when  moistened  with  an  acid,  to  a  metallic  state ;  whilst  when 
heated  with  the  carbonates  or  hydrates  of  sodium  and  potassium 
or  calcium,  the  chlorine  unites  with  the  alkali,  pure  silver  being 
set  free.  It  is  soluble  in  solutions  of  the  same  salts  as  the 
bromide,  and  also  in  ammonia — a  double  salt,  ammonio-chloride 
of  silver,  being  formed.  It  is  used  for  making  lantern-plate 
emulsions,  gelatino-chloride  printing-out  papers,  and  is  the 
sensitive  salt  in  albumen  paper. 

Silver  Chromate  (Ger.,  Chromsaurcs  Silberoxyd;  Fr,  Chro- 
mati  d'argent ;  Ital.,  Cromato  d'argentd).  Ag2Cr04  =  332.  An 
orange-red  precipitate,  formed  by  mixing  chromate  or  bichromate 
of  potassium  with  silver  nitrate.  It  was  suggested  by  Biny  lor 
emulsion  making,  and  by  Burton  as  an  admixture  with  brumidc 
emulsion  to  stop  halation. 

401  D  D 


Sil] 


DICTIONARY  OF  PHOTOGRAPHY. 


Silver  Citrate  (Ger.,  Silbercitrat,  Citronensaures  Silberoxyd; 
Fr.,  Citrate  d 'argent ;  Ital.,  Citrate  d'argento).  AgC6H507  =  297. 
This  can  be  obtained  in  small  quantities  by  adding  citric  acid  to 
silver  nitrate,  but  more  easily  by  double  decomposition  of  a 
soluble  citrate  and  silver  nitrate.  It  forms  white  crystals,  which 
are  soluble  in  water.  It  was  suggested  by  Monckhoven  for 
gelatino-bromide  emulsion,  but  its  chief  use  is  in  the  gelatino- 
chloride  printing-out  papers. 

Silver  Fluoride  (Ger.,  Fluorsilber ;  Fr.,  Fluorure  d' argent; 
Ital.,  Fluoncro  d'argento).  AgF  =  127.  This  salt  is  formed  by 
solution  of  silver  oxide  or  carbonate  in  hydrofluoric  acid,  not  by 
double  decomposition  of  silver  nitrate  and  a  soluble  fluoride. 
It  is  fairly  stable  in  light,  and  very  soluble  in  water.  It  has 
been  suggested  for  use  in  emulsions  for  development  and 
printing-out,  but  has  not  come  into  general  practice. 

Silver  Iodide  (Ger.,  Iodsilber,  Silberiodid ;  Fr.,  Iodurc ' 
d'argent;  Ital.,  Ioduro  d'argento).  Agl  =  235.  This  salt  can  be 
formed  in  an  analogous  manner  to  the  chloride,  either  by  direct 
union  or  double  decomposition,  using  iodine  and  iodide  instead 
of  chlorine  and  chloride.  When  prepared  by  precipitation  from 
a  solution  of  an  alkaline  iodide  with  nitrate  of  sliver,  the  alkaline 
iodide  being  in  excess,  a  white  precipitate  is  caused,  which  is  not 
so  sensitive  to  light  as  when  excess  of  nitrate  of  silver  is  used, 
when  the  precipitated  iodide  is  lemon-coloured.  Iodide  of  silver 
is  insoluble  in  water  and  dilute  nitric  acid,  almost  insoluble  in 
ammonia,  but  soluble  in  all  the  other  salts  which  dissolve 
bromide.  When  iodide  of  silver  is  dissolved  in  excess  of  solu- 
tion of  an  alkaline  bromide,  iodide,  or  chloride,  a  double  salt  is 
formed,  and  on  addition  of  water  the  resulting  solution  im- 
mediately precipitates  the  iodide.  It  is  used  for  making 
emulsions,  giving  extremely  sensitive  emulsions  and  great 
latitude  of  exposure,  with  great  density  of  image,  and  is  also 
used  iu  the  wet  collodion  process. 

Silver  Nitrate  (Ger.,  Silbe?'nitrat,  Salpetersaures  Silberoxyd ; 
Fr.,  Azotate  d 'argent ;  Ital.,  Azotato  a'argento).  AgNOs  =  170. 
Is  prepared  from  pure  silver  by  solution  in  nitric  acid,  and  sub- 
sequent purification  and  crystallisation.  Ordinary  commercial 
nitrate  is  usually  very  acid,  due  to  its  not  being  absolutely  freed 

402 


DICTIONARY  OF  PHOTOGRAPHY. 


[Sil 


from  nitric  acid;  but  that  prepared  for  photographic  purposes 
should  be  almost  neutral,  or  at  least  show  only  a  faint  trace  of  acid. 
To  the  dry-plate  operator  nitrate  of  silver  is  hardly  of  so  much 
interest  as  it  was  to  the  operator  of  the  wet-plate  process  ;  but 
to  those  who  desire  to  make  their  own  plates,  a  pure  salt  is  a 
sine  qua  non ;  and  as  the  testing  of  this  salt  is  almost  beyond 
the  ordinary  capabilities  of  the  dry-plate  workers,  the  only 
recommendation  which  the  author  can  give  is  to  buy  the  salt 
from  a  respectable  photographic  chemist,  and  to  pay  a  fair  price 
for  it,  as  the  author  has  in  his  possession  a  sample  of  nitrate 
bought  at  a  low  price,  25  per  cent,  of  which  is  nitrate  of 
potassium.  Solubility :  100  grains  are  soluble  in  50  minims 
of  distilled  water,  and  will  measure  80  minims :  1  in  1 5  of 
rectified  spirit.  When  dissolved  in  common  water,  a  thick 
curdy-white  precipitate  of  carbonate  and  chloride  of  silver  is 
formed.  Boiling  alcohol  dissolves  about  one-fourth  of  its  weight 
of  nitrate  of  silver,  but  deposits  it  on  cooling.  It  is  soluble  in 
ammonia,  with  the  formation  of  a  double  salt.  It  is  used  for 
sensitising  paper,  and  preparing  all,  or  nearly  all,  the  other  salts 
of  silver  used  in  photography.  When  heated  it  melts,  and 
forms,  when  poured  into  moulds,  the  lunar  caustic  of  commerce  ; 
and  when  heated  higher  still  gives  off  some  oxygen,  and  a 
mixture  of  nitrite  (AgN02)  and  nitrate  of  silver  (AgN03)  is  left. 
When  exposed  to  the  light,  either  in  solution  or  in  a  pure  dry 
state,  no  action  takes  place ;  but  on  contact  with  organic  matter 
it  darkens  through  purple  to  black. 

Silver  Oxide  (Ger.,  Silbcroxyd ;  Fr.,  Oxyde  d' argent;  Ital., 
ossido  d'argent).  Ag20  =  232.  May  be  obtained  by  adding  pure 
solution  of  any  caustic  alkali,  except  ammonia,  to  a  solution  of 
nitrate  of  silver,  when  the  oxide  is  precipitated  as  a  brownish 
black  precipitate.  It  is  but  little  used  now,  except  to  purify 
silver  solutions  from  copper,  but  was  used  in  the  old  wet-plate 
process  to  purify  the  silver  bath.  It  cannot  be  made  by  heating 
silver  in  a  current  of  oxygen  or  air,  because,  although  union  takes 
place,  the  whole  of  the  oxygen  is  given  up  on  cooling. 

Silver  Sulphide  (Ger.,  Schwcfclsilhcr ;  Fr.,  Sulfur*  <? argent; 
Ital.,  Solfuro  dargento).  Ag2S  =  242.  This  salt  is  met  w  ith  in 
residue  recovery,  and  is  the  resultant  salt  of  the  decomposition 
of  hyposulphite  of  silver  in  prints.    It  is  insoluble  in  water,  but 

403 


Sod] 


DICTIONARY  OF  PHOTOGRAPHY. 


soluble  in  every  solvent  of  the  other  silver  salts,  except  nitric 
acid,  which  converts  it  into  nitrate  and  sulphate. 

Sodium  Acetate  (Ger.,  Essigsaures  Natron,  Natriumacetat  ; 
Fr.,  Acetate  de  soude ;  Ital.,  Acetato  di  soda).  NaC2H302,  3H.X) 
=  136.  Can  be  prepared  -  by  neutralising  acetic  acid  with  car- 
bonate or  hydrate  of  sodium.  Solubility  :  1  in  3  of  cold  water, 
1  in  1  of  hot  water ;  soluble  also  in  alcohol.  It  is  a  slightly 
alkaline  salt,  and  is  used  principally  in  toning. 

Sodium  Bicarbonate  (Ger.,  Natriumbicarbonat,  Doppelt- 
kohlensaures  Natron ;  Fr.,  Bicarbonate  de  soude;  Ital.,  Bicar- 
bonate di  soda).  NaHC03  =  84.  Synonyms:  Sesqui-carbonate 
of  Soda,  Acid  Carbonate  of  Soda,  Hydrosodic  Carbonate.  Is 
prepared  by  passing  carbonic  acid  gas  into  carbonate  of  soda 
moistened  with  water.  Solubility :  1  in  10  of  water ;  insoluble 
in  alcohol.  When  heated  or  dissolved  in  boiling  water,  some 
carbonic  acid  gas  is  given  off,  water  and  carbonate  of  soda  being- 
formed. 

2NaHC03  =  Na2C03  +  H20  +  CO* 

It  is  used  for  toning.  It  is  invariably  met  with  in  commerce  as 
a  fine  impalpable  powder,  and  should  not  be  confounded  with 
the  carbonate  which  is  usually  met  with  in  crystals.  It  is  far 
less  soluble  than  the  carbonate. 

Sodium  Carbonate  (Ger.,  Kohlensiiures  Natron,  Natrimn- 
carbonat,  Soda;  Fr.,  Carbonate  de  soude;  Ital,  Carbonato  di 
soda).  Na2C03, ioH20  =  286.  Synonyms:  Washing  Soda,  Sal 
Soda,  Soda  Crystals,  Carbonate  of  Soda.  This  is  prepared  by 
several  methods,  which  depend  upon  the  decomposition  of  salt 
primarily.  Solubility :  60  per  cent,  in  cold,  445  per  cent,  in  hot 
water,  insoluble  in  alcohol,  and  98  per  cent,  in  glycerine.  Heat 
has  no  effect  upon  it,  except  to  drive  off  the  water  of  crystallisa- 
tion. The  commercial  varieties  of  this  salt  are  very  numerous, 
but  there  are  practically  only  two  which  need  trouble  the  photo- 
grapher ;  the  one  is  the  ordinary  washing  soda  of  commerce,  which 
is  of  indefinite  strength,  and  usually  contains  several  impurities, 
and  the  other  the  pure  salt,  the  sodium  carbonate,  which  has 
the  formula  given  above,  and  which  is  the  official  salt  of  the 
pharmacopoeia,  and  can  be  obtained  at  any  chemist's.    This  is 

404 


DICTIONARY  OF  PHOTOGRAPHY. 


[Sod 


the  only  salt  which  should  be  used  for  photography.  The 
common  washing  soda,  when  used  for  developing,  produces  a 
very  deep  yellow  stain,  which  is  ineradicable.  Tables  of  the 
equivalent  values  of  the  various  carbonates  will  be  found  in  the 
Appendix. 

Sodium  Chloride  (Ger.,  Chlomatrium,  Natriumchlorid,  Kock- 
salz,  Edclsah ;  Fr.,  Chlorure  de  sonde,  Chlorure  sodique^  Sel  de 
cuisine,  Selgemme;  Ital.,  Cloruro  disodio,  Sale  comune).  NaCl  = 
58*5.  Synonyms  :  Salt,  Sea  Salt,  Bay  Salt,  Rock  Salt,  Sal  Gemme. 
This,  the  most  abundant  source  of  sodium,  occurs  native  in  very 
large  deposits  in  Cheshire,  Galicia,  and  Eastern  Russia,  also  in 
sea  water,  which  contains  about  3  per  cent.  Solubility  :  35  per 
cent,  in  cold,  39*6  per  cent,  in  hot  water,  insoluble  in  absolute, 
but  sparingly  soluble  in  dilute,  alcohol,  insoluble  in  ether. 
Ordinary  salt  is  usually  contaminated  with  traces  of  sulphate  of 
soda  and  chloride  of  magnesium,  which  make  it  hygroscopic. 
Salt  is  used  for  precipitating  silver  from  print  washings,  for 
milking  gelatino-chloride  emulsions,  and  salting  positive  papers. 

Sodium  Citrate  (Ger.,  Natriumcitrat,  Citronensdures  Natro?i; 
Fr.,  Citrate  de  sodiu?n ;  Ital.,  Citrato  di  soda).  Na3CcH.07H20 
=  276.  Made  by  neutralising  citric  acid  with  carbonate,  bi- 
carbonate, or  hydrate  of  sodium,  evaporating,  and  crystallising 
the  resulting  solution.  Solubility :  1  in  1  of  water ;  sparingly 
soluble  in  alcohol.  It  is  used  sometimes  as  a  Restrainer  {q.v. ), 
and  also  in  preparing  some  printing-out  emulsions. 

Sodium  Hyposulphite  (Ger.,  Natriumtliiosulfat,  Fin 'matron, 
Untcrschwefligsiimrs  Natron,  Fixirsah;  Yx.,Hyposulfite  de  sonde, 
Thiosulfate  de  sonde;  Ital.,  Iposolfitc  di  soda).  N^SX^H-jO  = 
248.  Synonym  :  Thiosulphate  of  Soda.  This  important  salt  is 
formed  by  passing  sulphurous  acid  gas  through  sulphide  of 
sodium  until  no  further  precipitation  of  sulphur  occurs,  or  it  may 
be  made  by  heating — not  boiling — sulphite  of  sodium  with  excess 
of  sulphur,  and  commercially  by  treating  tank  waste  or  calcium- 
sulphide.  It  is  met  with  in  commerce  as  large  watery  crystals, 
which  should  be  entirely  free  from  acid  or  any  yellow  tinge.  It 
is  soluble  1  in  2  of  cold  water,  1  in  1  of  boiling  water,  and 
insoluble  in  alcohol.    Its  importance  in  a  photographic  sense,  as 

405 


Sod] 


DICTIONARY  OF  PHOTOGRAPHY. 


a  solvent  for  the  unacted-upon  silver  salts,  was  discovered  by 
Sir  William  Herschel.  When  a  salt  of  silver  is  added  to  hypo- 
sulphite, two  salts  are  formed,  as  shown  in  the  following 
equations : — 

AgCl     +      Na2S203     =     AgNaS2Os      +  NaCl. 
Silver  Sodium  Double  hypo-  Sodium 

chloride        hyposulphite  —      sulphite  of  chloride. 

silver  and  sodium 

And 

2AgCl  +  3Na2S203  =  Ag2Na43(S,03)  +  2NaCl. 
Silver  Sodium  Hyposulphite  Sodium 

chloride  hyposul-    ~~  of  sodium  and  chloride, 

phite  silver 

The  first  salt,  AgNaS203,  is  almost  insoluble  in  water,  and 
soluble  in  hyposulphite  of  soda  ;  therefore  excess  of  hypo  should 
always  be  used  for  fixing :  the  incomplete  elimination  of  this 
insoluble  salt  is  one  of  the  chief  causes  of  fading  in  prints.  To 
test  whether  the  whole  of  the  hyposulphites  are  eliminated  either 
by  washing  or  by  the  use  of  an  eliminator,  the  following  may  be 
used  : — 

Potassium  permanganate       ...     2  grs.  or        0*2  grm. 
Potassium  carbonate    ...       ...    20  ,,    ,,        2  grms. 

Distilled  water  40  ozs.  „  1,000  c.cm. 

A  few  drops  of  this  pinkish  purple  liquid  should  be  added  to 
the  last  washing  water,  when,  if  hypo  be  present,  a  greenish 
tinge  will  make  its  appearance  ;  or  a  few  drops  of  the  last  wash- 
ing water  may  be  added  to  a  solution  of  mercuric  chloride, 
when  a  cloudiness  will  make  its  appearance  if  hypo  be  present. 
Another  test  is  by  making  a  little  starch  paste  by  boiling  a  pinch 
of  starch  in  distilled  water,  and  adding  a  drop  or  two  of  solution 
of  iodine  in  alcohol  to  it,  when  a  deep  blue  coloration,  due  to 
iodide  of  starch,  will  make  its  appearance.  A  drop  or  two  of 
this  deep  blue  liquor  may  be  added  to  the  last  washing  water, 
when,  if  hypo  be  present,  the  blue  colour  will  be  destroyed 
The  addition  of  any  acid  to  a  solution  of  hyposulphite  will  cause 
evolution  of  sulphurous  acid  and  deposition  of  sulphur;  hence 

406 


DICTIONARY  OF  PHOTOGRAPHY. 


[Sph 


will  be  seen  the  necessity  of  making  the  fixing  bath  for  prints 
distinctly  alkaline,  to  prevent  snlphnration. 

Sodium  Nitrate  (Ger.,  Nahiumnitrat,  Salpetersaures  Natron; 
Fr.,  Azotate  de  soude ;  Ital.,  Azotato  di  soda).  NaNo3  =  85. 
Synonym  :  Chili  Saltpetre.  This  occurs  native  in  Chili,  and  has 
been  recommended  as  an  addition  to  developers  to  give  a  good 
chocolate  colour  to  negatives.  Solubility:  1  in  1*2  of  water; 
soluble  1  in  37  parts  of  alcohol. 

Sodium  Phosphate  (Ger.,  Phosphorsaures  Natron,  Natriu?n- 
phosphat,  Perlsalz ;  Fr.,  Phosphate  de  soude ;  Ital.,  Fosfato  di 
soda).  Na2HP04i2H20  =  358.  Prepared  by  neutralising  phos- 
phoric acid  with  any  alkaline  salt  of  soda.  Solubility  :  1  in  4  of 
cold,  1  in  2  of  boiling  water;  insoluble  in  alcohol.  On  exposure 
to  the  air  the  crystals  effloresce — that  is,  give  up  some  molecules 
of  water — and  it  is  questionable  whether  a  complex  phosphate  is 
not  formed.    It  is  used  for  toning. 

Sodium  Sulphite  (Ger.,  Schwefiigsdures  Natron,  Natrium- 
sulfit ;  Fr.,  Sulfite  de  soude ;  Ital.,  Solfito  di  soda).  Na2S03,7H20 
=  252.  Is  prepared  by  passing  sulphuric  acid  gas  through 
carbonate  of  soda  in  concentrated  solution  till  saturation.  Solu- 
bility :  1  in  4  of  cold  water,  1  in  1  of  hot  water ;  insoluble  in 
alcohol.  It  is  used  as  a  preservative  of  pyrogallol,  as  it  absorbs 
oxygen,  and  is  converted  into  sulphate.  This  salt  is  difficult  to 
keep  as  pure  sulphite,  but  keeps  better  in  concentrated  solutions 
than  weak  ones.  It  has  also  been  recommended  as  a  fixing 
agent;  but  as  its  powers  are  considerably  less,  and  its  price 
greater  than  hyposulphite,,  it  is  never  likely  to  come  into  general 
use. 

Sodium  Tungstate  (Ger.,  IVo/framsdures  Natron;  Fr., 
Tungstate  de  soude ;  Ital.,  Ttmgstato  di  soda).  Na2W04,  2HX) 
=  317.  A  combination  of  tungstic  acid  and  soda,  crystallising 
in  rhombic  plates.  Solubility  55  per  cent,  in  cold  water,  124 
per  cent,  in  hot  water ;  insoluble  in  alcohol.  It  is  used  in 
Toning  {q.v.). 

Spherical  Aberration.  When  a  simple  convex  lens  and 
short  focus  is  used  to  project  an  image  on  to  a  focussing  screen 
it  will  be  found  that  the  image  is  nowhere  absolutely  sharp  ;  and 
the  reason  of  this  indistinctness  is  spherical  aberration.  Let 

407 


Sph] 


DICTIONARY  OF  PHOTOGRAPHY. 


L,  fig.  94,  represent  a  short-focus  convex  lens,  and  r'r'r  r  repre- 
sent rays  of  light  striking  the  lens  ;  the  marginal  rays  r  r  cross 
the  axis  of  the  lens  or  come  to  a  focus  at  f ,  a  point  nearer  the  lens 
than  the  central  rays,  r'r'  ;  so  that  if  an  image  at  /  be  examined 


Fig.  94- 


it  will  be  seen  to  be  surrounded  by  an  aureola  or  ring  of  light,  ab, 
which  is  formed  by  the  spreading  of  the  marginal  rays  after 
meeting  at  the  focus  f.  This  ring  is  called  lateral  spherical 
aberration,  and  the  diameter  of  the  same  is  termed  the  expression 
the  lateral  aberration.    The  distance  along  the  axis  of  the  lens 


between  the  principal  focus,  or  the  focus  of  the  central  rays,  R  r'' 
at/  and  the  focus  of  the  marginal  rays,  r  r,  at  /',  is  called  longi- 
tudinal aberration.  In  this  case  the  focus  of  the  marginal  rays» 
being  shorter  than  that  of  the  central  rays,  the  aberration  is 
called  positive  spherical  aberration.    The  circle  of  least  confusion 

408 


DICTIONARY  OF  PHOTOGRAPHY. 


[Sph 


or  least  aberration,  or  the  smallest  section  it  is  possible  to  make 
of  the  cone  of  rays,  is  situated  between J~"  and In  negative 
or  divergent  lenses  the  central  rays,  r'  r',  emerge  in  the  direction 
b  b,  and  the  marginal  rays,  r  r,  in  the  direction  d  d.  The  central 
rays  prolonged  cut  the  axis  at /,  which  is  then  the  principal  focus, 
and  the  marginal  rays  produced  cut  the  axis  at /'  ;  therefore  the 
focus  of  the  marginal  rays  is  longer  than  that  of  the  central  rays 
and  this  is  termed  negative  spherical  aberration.  The  sphericity 
of  the  surfaces  of  a  lens  being  the  cause  of  spherical  aberration, 
it  necessarily  follows  that  the  more  curved  these  surfaces  are 


/ 


u 

si 

J  . 

J' 

/i 

Fig.  96. 


relative  to  the  diameter  of  the  lenses  the  greater  is  the  spherical 
aberration  ;  thus,  lenses  of  comparatively  short  focus  and  large 
aperture,  like  portrait  lenses,  are  more  likely  to  suffer  from 
spherical  aberration.  Any  divergent  or  convergent  lens  suffering 
from  this  defect,  in  a  greater  or  less  degree,  may  be  cured  to  a 
great  extent  by  placing  a  diaphragm  or  stop  in  front  of  the  lens, 
which  actually  reduces  the  lens  to  a  smaller  working  aperture, 
and  thus  prevents  the  marginal  rays  from  being  refracted  by  the 
lens.  The  use  of  the  diaphragm,  however,  will  not  completely 
cure  spherical  aberration.  It  reduces  it,  it  is  true,  to  a  negligable 
quantity;  thus  let  In,  fig.  96,  represent  a  convex  lens;  it  is 
obvious  that  the  marginal  rays  will  be  refracted  and  meet  at  / 

409 


Sul] 


DICTIONARY  OF  PHOTOGRAPHY. 


whereas  the  central  rays  cross  the  axis  aaatf,  farther  from  the 
lens  ;  by  the  insertion  of  a  diaphragm  the  marginal  rays  are 
prevented  from  reaching  the  lens,  and,  therefore,  only  the  central 
rays  are  used  to  form  the  image.  Certain  portrait  lenses  and  others 
have  been  placed  on  the  market,  by  means  of  which  a  certain 
amount  of  spherical  aberration  is  designedly  left  outstanding  or 
can  be  introduced  at  will,  giving  the  so-called  diffusion  of  focus. 
Spherical  aberration  may  be  detected  in  a  lens  by  very  simple 
tests,  and  its  effect  is  to  render  the  image  upon  the  focussing 
screen  indistinct,  so  that  it  is  impossible  to  focus  accurately 
either  the  centre  or  the  margins.  An  easy  test  is  :  To  a  window 
affix  two  small  circles  of  opaque  paper  so  as  just  to  touch  each 
other,  and  having  focussed  these  on  the  centre  of  the  screen, 
insert  a  diaphragm  by  the  aid  of  a  focussing  magnifier,  and  see 
whether  the  images  gain  in  sharpness.  If  they  do,  spherical 
aberration  has  not  been  totally  eliminated.  Another  method  is 
to  cut  a  piece  of  opaque  paper  the  exact  size  of  the  lens,  and 
then  cut  the  centre  of  this  circle  out,  so  as  to  leave  a  ring  about 
one-seventh  the  diameter.  Then  lightly  affix  this  ring  to  the 
front  of  the  lens,  and  focus  a  sheet  of  newspaper,  or  the  two 
circles  of  paper  mentioned  above;  then  remove  the  ring  and 
affix  the  central  circle  to  the  lens,  and  again  focus.  There  should 
be  no  alteration  of  focus  if  there  is  spherical  aberration  present. 

Sulpho-Pyrogallol.  A  term  given  to  a  solution  of  pyro- 
gallic  acid  in  conjunction  with  a  sulphite,  as  first  suggested 
by  Berkeley.    The  original  formula  was  : — 

Pyrogallol    I  oz. 

Sodium  sulphite     ...       ...       ...       ...       4  ozs. 

Citric  acid   |  oz. 

Water   ,    9  ozs. 

Sulphuric  Acid  (Ger.,  Schwefelsciure ;  Fr.,  Acide  Sulfuriqtte). 
H2S04=98.  It  is  prepared  by  roasting  iron  or  copper  pyrites 
and  oxidising  the  products.  Specific  gravity  :  r845.  It  is  used 
in  photography  as  a  clearing  agent,  and  for  preserving  solution 
of  ferrous  sulphate.  It  forms  soluble  salts  called  sulphates.  It 
is  extremely  corrosive  and  caustic.  When  taken  undiluted 
internally  it  is  poisonous,  the  antidotes  being  the  same  as  for 
nitric  acid.  It  is  miscible  with  water  in  all  proportions.  Great 
heat  is  evolved  when  thus  mixed,  the  water  being  raised  to  nearly 

410 


DICTIONARY  OF  PHOTOGRAPHY. 


[The 


boiling  point ;  great  care,  therefore,  should  be  used  in  mixing  it, 
or  the  measure  or  vessel  may  be  broken. 

Sulphurous  Acid  (Ger.,  Schwefligwasserstoffsaure ;  Fr., 
Acide  Sulfurettx).  H2S03=82.  Prepared  by  deoxidising 
sulphuric  acid  with  charcoal.  It  is  a  colourless  liquid,  with 
pungent  sulphurous  odour,  and  contains  5  per  cent,  of  sulphur- 
ous anhydride,  S02.  Specific  gravity,  vo2$.  It  should  be  freshly 
prepared,  as  it  changes  by  keeping  into  sulphuric  acid.  It  is 
recommended  for  preserving  pyrogallol,  and  forms  one  of  the 
ingredients  of  Beach's  Developer  (q.v.).  Care  should  be  exercised 
in  handling  this,  not  to  inhale  the  fumes,  which  are  extremely 
poisonous. 

Talbotype.   See  Calotype. 

Tannic  Acid  (Ger.,  Gerbsaure;  Fr.,  Tannin).  C27H22017=6i8. 
This  is  not  a  true  acid,  but  a  glucoside  obtained  from  galls. 
Solubility  :  10  in  8  of  water,  10  in  8  of  alcohol,  sparingly  soluble 
in  ether,  its  photographic  use  being  limited  almost,  if  not  entirely, 
to  the  old  collodion  process. 

Tartaric  Acid  Ger.,  Weinsteinsiiurc ;  Fr.,  Acide  Tariaiique). 
H2C4H206  =  1 50.  Prepared  from  the  impure  cream  of  tartar  in 
the  lees  of  wine  by  precipitation  by  chalk,  and  subsequent  addition 
of  sulphuric  acid.  Solubility:  1  in  -66  of  cold  water,  1  in  5 
of  boiling  water;  soluble  also,  in  alcohol  and  ether.  Its  use  in 
photography  is  limited,  being  sometimes  used  instead  of  citric 
acid,  and  for  preserving  sensitised  paper. 

Test  Papers.  Small  slips  of  bibulous  paper  soaked  in  a  solu- 
tion of  litmus  or  other  dye,  and  used  for  testing  any  liquid  for 
its  alkalinity  or  acidity. 

Thermometer  is  an  instrument  used  for  determining  the 
temperatures  of  different  substances,  liquids,  and  gases.  These 
instruments  are  so  generally  known  that  but  little  description  is 
needed  ;  but,  as  several  different  methods  of  marking  them  are 
in  vogue,  the  following  explanation  and  rules  may  make  all 
clear  : — There  are  three  principal  methods  of  division — Reaumur, 
Celsius  or  Centigrade,  and  Fahrenheit.  Reaumur  takes  o° 
as  the  temperature  of  freezing  water,  and  divides  the  scale 
between  this  point  and  boiling  water  into  8o°.  This  system 
is  generally  dying  out.    Centigrade  or,  Celsius'  system,  starts 

4it 


Thi] 


DICTIONARY  OF  PHOTOGRAPHY. 


from  o°  as  the  freezing  point  and  ioo°  as  the  boiling 
point.  This  system  is  gradually  gaining  ground.  Fahrenheit's 
system  takes  32°  as  the  freezing  point  and  21 2°  as  the 
boiling  point.  This  is  the  system  in  common  use  in  England, 
and,  notwithstanding  many  objections,  is  one  of  great  value, 
because  of  the  number  of  divisions  of  the  scale.  To  convert 
degrees  of  one  scale  into  those  of  another  the  following  rules 
must  be  used  : — 

To  convert  Reaumur  into  Centigrade. 
Multiply  by  5  and  divide  by  4. 

Example  :  8o°  R  X  5  -r  4  =  ioo°  C. 

To  convert  Reaumur  into  Fahrenheit. 

Multiply  by  9  and  divide  by  4,  and  add  32. 

Example:  8o°  R.  X  9  -f  4  +  32  =  212°  F. 

To  convert  Centigrade  into  Reaumur. 
Multiply  by  4  and  divide  by  5. 

Example:  ioo°  C.  X  4  -i-  5  =  8o°  R. 

To  Convert  Centigrade  into  Fahrenheit. 

Multiply  by  9,  divide  by  5,  and  add  32  to  the  result. 

Example:  ioo°  C.  x  9 -r- 5  +  32=212°  F. 

To  Convert  Fahrenheit  into  Reaumur. 

Subtract  32,  multiply  by  4,  and  divide  by  9. 

Example:  21 2°  F.    32  x  4 -—9=80°  R. 

To  Convert  Fahrenheit  into  Centigrade. 
Subtract  32,  multiply  by  5,  and  divide  by  9. 

Example:  2120  F.-32  x  5-r9  =  ioo°  C. 

Thinness  Of  Negative.  This  may  be  the  effect  of  three 
causes  :  first,  under-exposure  ;  second,  over-exposure  ;  and  third, 
under-development.  Thinness  from  under-exposure  is  usually 
caused  by  the  whole  plate  veiling  over  before  sufficient  density 
can  be  obtained,  due  to  the  use  of  excessive  alkali  (See  Under- 
exposure). In  the  case  of  over-exposure  it  is  due  to  the 
energetic  action  of  the  developer,  consequent  upon  the  too  great 

412 


DICTIONARY  OF  PHOTOGRAPHY. 


[Tit 


action  of  light  (see  Over-Exposure).  In  under-development 
the  result  is  thinness,  consequent  upon  the  developer  not 
reducing  sufficient  silver  salt  to  the  metallic  state.  This  is 
generally  distinguished  from  over-  or  under-exposure  by  the 
absence  of  fog  or  veiling. 

Thiocarbamid  (Ger.,  Siilphoharnstoff,  Thiocarbamid ;  Fr. 
and  Ital.,  Thiocarbamid).  Synonym,  Thiourea.  C4H4N-,S.  This 
organic  compound  was  proposed  by  Dr.  Bogisch  as  a  fixing  agent 
for  chloride  of  silver,  but  its  great  utility  is  for  the  removal  of 
stains  of  pyro  or  other  developers,  for  removing  green  fog  and 
silver  stains,  for  which  purpose  the  following  solutions  are 
recommended. 

Thiocarbamid         ...       ...       ...       ...  20  grs. 

Citric  Acid   10  ., 

Water         ...       ...       ...    2  ozs. 

or, 

Thiocarbamid         ...       ...       ...       ...  20  grs. 

Alum  ...       ...       ...    20  ,, 

Acetic  Acid   10  minims. 

Water    2  ozs. 

Thiosinamin(Ger.,  Allyhulphohariistojf,  Thiosinamin;  Fr.  and 
Ital.,  Thiosinamin).  Synonym :  Allylsulphurea.  CSNH2NHC3H- 
is  an  organic  compound  obtained  by  the  action  of  ammonia  on 
oil  of  mustard.  It  was  suggested  by  Liesegang  as  a  fixing  agent 
for  chloride  of  silver,  but  it  has  not  come  into  general  use. 

Titles  Oil  Prints.  Numerous  dodges  have  been  suggested 
for  this,  such  as  writing  backwards  on  the  negative,  employing 
type,  carbon  tissue,  etc.  The  most  practical  methods  are 
either  to  write  the  title  first  of  all  on  the  paper  before  printing 
with  some  aqueous  non-actinic  or  opaque  colour,  such  as 
gamboge  or  Indian  Ink,  the  same  being  washed  off  prior  to 
toning ;  or  the  following  may  be  used  after  toning  : — 


Iodide  of  potassium  ...       ...       ...       ...  10  parts 

Water   30  „ 

Iodine   1  ,, 

Gum   1  ., 


Write  with  this  on  a  dark  portion  of  the  print,  when  the  letters 

413 


Ton] 


DICTIONARY  OF  PHOTOGRAPHY. 


will  soon  become  visible  by  the  conversion  of  the  image  into 
iodide  of  silver,  which  will  be  dissolved  by  the  usual  fixing 
bath. 

Toning.  If  a  silver  print  is  placed  direct  into  the  fixing  bath 
an  unpleasant  brick-red  colour  is  the  result.  The  operation 
of  toning  consists  in  changing  this  colour  by  the  partial  sub- 
stitution of  gold  or  some  other  metal  for  the  silver  in  the  print. 
The  chemistry  involved  in  toning  is  comparatively  simple,  all 
toning  baths  contain  gold  in  such  a  state  that  it  is  readily 
deposited  upon  any  reducing  substance  which  may  be  placed 
in  it.  There  are  practically  three  conditions  of  toning  bath 
to  consider;  first,  the  acid,  secondly,  the  neutral,  and,  thirdly, 
the  alkaline  toning  bath.  At  the  present  time  the  acid  bath  is 
but  little  used;  it  strongly  attacks  the  image,  gives  bluish 
tones,  and  causes  very  slow  toning.  When  a  weak  acid,  such 
as  acetic,  boric,  or  phosphoric,  is  added  to  a  neutral  bath, 
the  tones  are  reddened  and  the  image  weakened.  When  in 
practice  a  neutral  salt,  such  as  acetate,  borate,  or  phosphate  of 
soda,  is  added  to  acid  solution  of  chloride  of  gold  the  hydrochloric 
acid  immediately  combines  with  the  base  and  sets  free  the 
weaker  acid.  The  second  class  of  toning  baths  are  those 
which  give  the  most  beautiful  purple  tones,  and  as  they  are 
comparatively  stable  they  may  be  used  over  and  over  again,  and 
strengthened  by  the  addition  of  more  neutral  solution  of  gold. 
The  third  class,  or  alkaline  baths,  have  a  tendency  to  give  rather 
more  bluish  shades  than  the  neutral.  The  addition  of  carbonate 
of  soda,  or  any  alkaline  carbonate,  to  solution  of  chloride  of  gold 
neutralises  the  free  acid,  chloride  of  sodium  being  formed  ;  and 
if  an  excess  of  alkali  be  present,  stable  compounds  of  gold 
are  formed,  which  are  not  reduced  by  silver.  If  no  alkali  be 
present  in  excess,  the  toning  power  lasts  longer,  only  toning 
takes  place  somewhat  more  slowly.  With  freshly  mixed  alkaline 
baths  it  is  stated  by  Lainer  and  Davanne  that  one  atom  of  gold 
only  replaces  three  atoms  of  silver. 

AuCla+  3Ag=3AgCl+Au. 

With  a  small  excess  of  alkali  the  chloride  of  gold  is  decomposed 
into  aurous  chloride  according  to  Davanne  and  Girard. 

AuCl + NaOH=AuCl + HCl+NaOCl. 
414 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ton 


And  an  old  bath  in  this  state,  for  the  change  takes  place  but 
slowly,  replaces  one  atom  of  silver  with  one  atom  of  gold. 

AuCl+Ag  AgCl+Au. 
And  the  prints  in  the  latter  case  are  most  vigorous  and 
permanent.  Finally,  the  toning  baths  become  quite  colourless 
and  will  not  tone.  Numerous  formulae  have  been  given  for 
toning  baths,  and  in  many  cases  merely  the  quantities  of  the 
salts  are  altered.  In  many  cases  the  new  formulas  are 
recommended  as  giving  exceptionally  fine  tones  or  possessing 
some  particular  property  which  in  many  cases  can  be  explained 
by  the  fact  that  the  addition  of  more  of  one  ingredient  may 
convert  the  bath  from  a  neutral  to  an  alkaline  one.  Mercier 
in  his  valuable  little  treatise  "Virages  et  Fixages  "  formulates 
the  following  rules  which  are  instructive. 

1.  When,  in  making  a  toning  bath,  ingredients  more  or  less 
alkaline  are  used,  the  proportion  of  such  ingredients  necessary 
to  decolorise  the  bath  is  less  the  more  alkaline  it  is.  Taking 
as  a  typical  bath  one  containing  chloride  of  gold  I  part,  water 
1,000  parts,  the  following  are  the  necessary  proportions  of  salts 
to  decolorise  the  bath  completely  in  six  hours,  caustic  potash 
07  parts,  potassium  bicarbonate  2  to  3  parts,  sodium  tungstate 
12  to  18  parts,  sodium  phosphate  25  to  30  parts,  borax  4  to  5 
parts.  When  only  slightly  soluble  substances  are  used,  then 
the  above  rule  should  read  :  When  a  solution  of  chloride  of 
gold  is  treated  with  a  substance  slightly  alkaline  and  slightly 
soluble,  the  decoloration  is  more  rapid  the  more  alkaline  the 
substance  is. 

2.  If  the  salts  employed  are  alkaline  oxides,  the  bath 
decolorises  and  becomes  fit  for  use  the  quicker  the  greater 
the  quantity  of  salt  employed. 

3.  All  neutral  or  slightly  alkaline  toning  baths  used  im- 
mediately they  are  colourless,  tone  very  rapidly  and  tend  to  give 
violet  black  tones. 

4.  All  neutral  or  slightly  alkaline  toning  baths  lose  their 
activity  gradually,  the  more  alkaline  the  bath  the  quicker  this 
takes  place. 

5.  Acid  toning  baths  (those  reddening  litmus  paper  very 
slowly)  do  not  become  colourless  when  made  with  pure  mineral 
salts;  those  prepared  with  organic  salts  become  colourless  when 
they  approach  neutrality,  or  when  prepared  with  reducing  salts. 

415 


Ton] 


DICTIONARY  OF  PHOTOGRAPHY. 


6.  Acid  toning  baths  preserve  their  toning  power  indefinitely, 
and  their  activity  is  greater  the  less  acid  they  are. 

7.  The  tones  obtained  with  the  different  papers  and  different 
baths  depend  upon  the  amount  of  gold  deposited ;  the  quicker 
the  prints  tone,  and  the  more  complete  the  toning  action,  the 
nearer  the  tone  approaches  to  a  blue  black. 

The  colour  obtained  by  toning  varies  with  each  bath,  and 
in  many  cases  with  each  different  brand  of  paper,  and  the  tone 
depends  to  a  great  extent,  too,  upon  the  negative.  Some 
authorities  even  state  that  the  tone  of  the  print  is  fixed  when 
the  plate  is  developed,  but  the  author  cannot  quite  bear  out 
this  statement.  Good  bold  negatives  with  plenty  of  contrast 
give  more  easily  purple  and  black  tones  than  weak  muddy 
negatives  devoid  of  any  contrast,  vigour,  or  sparkle.  The 
following  are  the  baths  most  commonly  used  at  the  present 
time,  with  some  notes  on  the  same : — 

1.  Acetate  Bath. 

Chloride  of  gold    1  gr.   or  -06  grm. 

Acetate  of  soda    30  grs.  „      2  grms. 

Distilled  water         ...       ...    10  ozs.  ,,  250  c. cm. 

Neutralise  the  gold  with  a  pinch  of  common  chalk  mixed  with 
\  oz.  of  water,  allow  to  settle,  pour  off  the  solution,  and  add  to 
the  acetate  dissolved  in  the  water.  The  bath  must  be  kept  at 
least  twenty-four  hours  before  use,  and  works  better  even  when 
older.  It  gives  brownish  purple  tones,  which  are  very  pleasing. 
The  bath  keeps  fairly  well  if  distilled  water  is  used,  and  if  no 
actinic  light  is  allowed  to  gain  access  to  it.  If  the  bath  be 
required  for  immediate  use,  hot  water  must  be  used,  and  the 
bath  may  be  used  as  soon  as  cold.  After  toning,  the  bath 
should  not  be  thrown  away,  but  filtered  and  kept  for  use  instead 
of  water  for  diluting  the  next  bath.  The  author  prefers  keeping 
a  concentrated  solution  as  follows  : — 

Chloride  of  gold    15   grs.  or     1  grm. 

Acetate  of  soda    480     ,,    „     30  grms. 

Distilled  water,  to  make      ...       7^  ozs.  ,,  200  c.cm. 

For  use,  mix  \  oz.,  equal  to  1  gr.  of  gold,  to  ^  pint  water  for 
every  sheet  of  paper  to  be  toned.  After  use,  the  bath  may  be 
filtered  and  preserved  to  dilute  the  next  bath. 

416 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ton 


2.  Bicarbonate  and  Acetate  Bath. 

Chloride  of  gold                           15  grs.  or     1  grm. 

Bicarbonate  of  soda    ...       ...  30  ,,     2  grms. 

Acetate  of  soda    360  24 

Distilled  water                             15  ozs.  400  c.cm. 

Add  the  gold  and  bicarbonate  of  soda  to  2  ozs.  of  water,  shaking 
occasionally,  and  keep  till  colourless ;  then  add  the  acetate  and 
remainder  of  water,  and  keep  for  six  hours,  and  dilute  as  for  the 
acetate  bath.  The  same  directions  apply  to  this  bath  as  to  No.  I. 
Rich  purple-black  tones  are  obtained. 

3.  Borax  Bath. 

Chloride  of  gold    1  gr.   or  -c6  grm. 

Borax    20  grs.  ,,      2  grms. 

Distilled  water   10  ozs.  „  250  c.cm. 

4.  Bicarbonate  Bath. 

Chloride  of  gold    1  gr.    or  -06  grm. 

Bicarbonate  of  soda    30  grs.  „      2  grms. 

Distilled  water   10  ozs.  „  250  c.cm. 

These  give  warm  brown  tones,  the  latter  inclining  to  purplish 
black.    They  can  be  used  as  soon  as  made,  but  will  not  keep. 

5.  Phosphate  Bath. 

Chloride  oi  gold    1  gr.    or  -06  grm. 

Phosphate  of  soda    20  grs.         2  grms. 

Distilled  water   10  ozs.  ,,  250  c.cm. 

Gives  warm  purplish  tones.  May  be  used  as  soon  as  mixed. 
Will  not  keep. 

6.  Compound  Bath. 
Stock  Solution. 

Borax   330  grs.  or   18  grms. 

Acetate  of  soda    180        ,,  10 

Bicarbonate  of  soda    90  ,,    ,,  6 

Distilled  water   20  ozs.     500  c.cm. 

417  E  E 


Ton] 


DICTIONARY  OF  PHOTOGRAPHY. 


Toning  Bath. 

Stock  solution   10  drms.  or  35  c.cm. 

Chloride  of  gold    1  gr.      „   -06  „ 

Distilled  water ...       ...       ...      10  ozs.       250  „ 

Mix  two  hours  before  using.  Retain  the  bath  after  each  toning, 
and  use  instead  of  water  for  new  toning  bath.  This  gives 
exceedingly  rich  brown  tones,  and  is  a  great  favourite  of  the 
author's. 

7.  Carbonate  Bath. 
Chloride  of  gold        ...       ...       1  gr.   or  *o6  grm. 

Carbonate  of  soda    15  grs.         1  ,, 

Distilled  water ...       ...       ...      10  ozs.  „  250  c.cm. 

Mix  half  an  hour  before  use.  Will  not  keep.  Tone  to  purplish 
blue,  and  fix.  The  resulting  colour  is  a  good  brown,  free  from 
any  purplish  tinge.  But  to  get  a  true  sepia  tone  use  water  at 
about  1700  F.,  add  the  gold,  and  use  in  ten  minutes. 

8.  Chloride  of  Lime  Bath. 

Chloride  of  gold    15  grs.  or     1  grm. 

Common  chalk...       ...       ...    150  „    „    10  grms. 

Chloride  of  lime         ...       ...      24  „    „   1*5  grm. 

Lime  water      ...       ...       ...      15  ozs.  ,,  400  c.cm. 

Add  the  gold  to  the  chalk,  and  mix  into  a  paste  with  a  little  lime 
water,  and  leave  for  one  hour ;  filter,  and  wash  the  filter  with 
the  remainder  of  the  lime  water  in  which  is  dissolved  the  chloride 
of  lime.  Add  1  oz.  of  the  above  to  10  ozs.  of  water  for  every 
sheet  of  paper  to  be  toned.  When  old,  and  the  bath  refuses  to 
tone,  add  a  little  chloride  of  gold,  and  leave  for  fifteen  minutes  ; 
or  if  no  smell  of  chlorine,  add  a  grain  of  chloride  of  lime.  This 
gives  purplish  black  tones,  and  keeps  well. 

9.  Acetate  and  Chloride  Bath. 

Chloride  of  gold    15  grs.  or     1  grm. 

Acetate  of  soda   360  „    ,,  23  grms. 

Chloride  of  lime    135   „    „      8  „ 

Common  chalk ...       ...       ...  360        ,,  23  „ 

Distilled  water..,    15  ozs.     400  c.cm. 

418 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ton 


The  directions  for  mixing  this  are  the  same  as  lor  the  chloride 
of  lime  bath,  the  acetate  being  added  in  solution  last.  This  gives 
warm  black  tones,  and  keeps  well. 

10.  Acetate  and  Borax  Bath. 

Chloride  of  gold    15  grs.  or     1  grm. 

Acetate  of  soda         ...       ...    150  ,,    ,,    10  grms. 

Borax    15        ,,      1  grm. 

Distilled  water  ...       ...       ...      15  ozs.  ,,  400  c. cm. 

Mix  the  gold  and  acetate  in  3  ozs.  of  water,  and  keep  for  six 
hours.  Add  the  borax  dissolved  in  remainder,  and  use  at  once. 
This  keeps  fairly  well,  and  gives  brownish  black  tones. 

11.  Carbonate  of  Lime  Bath. 
Chloride  of  gold         ...       ...      15  grs.  or     1  grm. 

Carbonate  of  lime  (chalk)  ...  75  ,,  ,,  3  grms. 
Distilled  water   15  ozs.  ,,  400  c.cm. 

Mix  the  gold  and  chalk  and  water,  and  leave  for  one  hour. 
Keeps  fairly  well,  and  gives  brownish  purple  tones. 

12.  Tungstate  Bath. 
Chloride  of  gold         ...       ...      15  grs.  or     1  grm. 

Tungstate  of  soda      ...       ...    300  ,,    „    20  grms. 

Distilled  water  (at  2120  F.)  ...      15  ozs.  ,,  400  c.cm. 

Use  when  cooled.  Gives  very  fine  purplish  brown  tones. 
Keeps  fairly  well.  Add  an  ounce  of  stock  bath  to  the  old  bath 
for  every  sheet  of  paper  used. 

13.  Uranium  Toning  Baths. 
Uranium  nitrate  I    r      ,  c 
Chloride  of  gold  [  of  each      -       1        or  '°6  grms" 

Bicarbonate  of  soda    20  grs.  ,,  1-3  „ 

Distilled  water  .. .       ...       ...      10  ozs.  ,,  250  c.cm. 

This  bath  must  be  used  as  soon  as  mixed,  and  should  be  dis- 
tinctly alkaline  in  test  papers.  It  gives  very  fine  purplish  black 
tones,  and  the  author  has  found  the  best  results  follow  complete 
elimination  of  free  silver  by  salt-and-water  bath  previous  to 
toning.  The  prints  when  toned  should  also  be  placed  in  salt 
and  water. 


Ton] 


DICTIONARY  OF  PHOTOGRAPHY. 


14. 

Chloride  of  gold    4  grs.  or  -25  grm. 

Uranium  nitrate         ...       ...     4   „       '2$  „ 

Chloride  of  sodium  (salt)      ...  60   „    ,,     4  grms. 

Acetate  of  sodium      ...       ...  60   „    „     4  „ 

Distilled  water  .. .       ...       ...  32  ozs.        1  litre. 

Neutralise  the  gold  and  uranium,  previously  dissolved  in  a  little 
water,  with  bicarbonate  of  soda.  The  prints  should  be  rather 
deeply  printed,  and  washed  free  from  silver,  and  then  toned. 
This  bath  gives  fine  blacks,  and  with  plain  or  matt-surfaced  paper 
the  results  can  hardly  be  told  from  bromide  prints.  The  follow- 
ing is  the  best  fixing  bath  for  this,  and  the  prints  should  be 
washed  in  salt  and  water  after  toning : — 

Hyposulphite  of  soda  ,  2  ozs.  or  50  grms. 

Salt    1  oz.    „    30  „ 

Bicarbonate  of  soda    i  »  7  » 

Water   1  pint  ,,  500  c.cm. 

Uranium  may  also  be  added  to  any  of  the  ordinary  gold  toning 
baths  in  use.  Thus  far  the  author  has  given  formulae  for  toning 
baths  which  he  has  tried,  and  can  speak  from  personal  experi- 
ence. The  following  were  baths  in  use  some  twenty  or  thirty 
years  back,  and  some  were  much  approved  of.  The  author  regrets, 
however,  that  he  has  not  had  time  to  experiment  with  them  : — 

15.  Lead  and  Gold  Bath. 

Nitrate  of  lead   30  grs.  or      2  grms. 

Chloride  of  sodium  (salt)      ...    40   „    „    2*5  „ 

Hyposulphite  of  soda  240        „     15  „ 

Chloride  of  gold        ...       ...      1  gr.   „    -06  grm. 

Distilled  water   10  ozs.  „   250  c.cm. 

Mix  in  warm  water.  Use  at  once.  Bath  won't  keep.  Gives 
rich  blacks.  Fix  in  fresh  hypo.  Permanency  of  tones  not 
guaranteed. 

16.  Bromide  Bath. 

Chloride  of  gold    1  gr.  or  -06  grm. 

Carbonate  of  soda    15  grs.  „      1  „ 

Sodium  bromide    ^  gr.   „   -03  ,, 

Distilled  water   10  ozs.  „  250  c.cm. 

420 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ton 


Use  at  once.  Won't  keep.  Gives  rich  brown  or  chocolate 
tones.    The  more  bromide  is  added  the  redder  the  tone. 

17.  Lime  Water  and  Acetate  Bath. 
Chloride  of  gold         ...       ...    15  grs.  or     1  grm. 

Acetate  of  soda   180   ,,    „  iigrms. 

Lime  water      ...       ...       ...    15  ozs.  „  400  c. cm. 

Gives  purplish  tones.    Keeps  fairly  well. 

18.  Sel  d'Or. 

Chloride  of  gold    1  gr.      or  -06  grm. 

Hyposulphite  of  soda  ...     4  grs.     ,,   -25  ,, 

Hydrochloric  acid       ...       ...     4  drops      '25  c.cm. 

Distilled  water   10  ozs.     „  250  „ 

Dissolve  the  gold  in  half  the  water,  and  add  to  the  hypo  dis- 
solved in  remainder  of  water,  stirring  constantly ;  then  add  the 
acid.  Burton  strongly  recommends  this  bath.  After  toning,  put 
prints  into  a  soda  bath  and  then  fix.  So  far  all  the  baths  given 
have  referred  to  ordinary  albumenised  paper.  The  following  are 
specially  recommended  for  printing-out  emulsions,  whether  on 
glass  or  paper,  such  as  Aristotype.  In  fact,  for  the  latter  paper 
these  are  the  only  baths  which  really  give  beautiful  results : — 

19.  Sulphocyanide  Bath. 
Chloride  of  gold         ...       ...      1  gr.   or  -06  grm. 

Sulphocyanide  of  potash       ...    12  grs.  ,.   75  ,, 
Hyposulphite  of  soda  ...       ...      \  gr.        -03  ,, 

Distilled  water ...       ...       ...     4  ozs.  „  100  c.cm. 

The  prints  should  be  rather  deeply  printed,  and  soaked  in  a 
solution  of  alum  (1  in  10)  first  for  five  minutes,  then  given  a  dip 
into  a  bath  of  carbonate  of  soda,  and  then  toned  faced  down- 
wards; afterwards  dipped  in  soda  and  fixed  in  fresh  hypo. 

20.  Fixing  and  Toning  Bath. 

Hyposulphite  of  soda   6  ozs.  or  186-0  grms. 

Sulphocyanide  of  potash       ...      1  oz.         30- 1  ,, 

Acetate  of  soda    i|  ozs.  ,,    46  0  ,, 

Alum   96  grs.  „      6  0  ,, 

Distilled  water ...    21  ozs.  ,,  6oo-o  ,, 


Ton] 


DICTIONARY  OF  PHOTOGRAPHY. 


Fill  the  bottle  containing  this  solution  with  clippings  of  paper  or 
bad  prints,  or  add  100  grs.  of  chloride  of  silver,  and  leave  for 
twenty-four  hours,  filter,  and  add 

Chloride  of  gold    15  grs.  or     1  grm. 

„  ammonium         ...    30  „    „     2  grms. 
Distilled  water   6  ozs.  ,,  170  c.cm. 

The  same  directions  for  using  this  bath  as  for  No.  19.  The  author 
prefers  the  use  of  No.  19,  and  fixing  separately,  as  with  this  there 
is  no  certainty  as  to  when  the  gold  is  exhausted  and  sulphur 
toning  begins.  The  prints  change  to  a  bright  yellow,  and  run  the 
scale  of  colours  to  a  brilliant  purplish  black.  Both  these,  Nos.  19 
and  20,  may  be  used  for  albumenised  paper  prints. 

A  few  Maxims  for  Toning.  Prints  should  be  thoroughly 
freed  from  free  silver,  except  in  the  case  of  all  baths  containing 
chloride  of  lime  and  sulphocyanides ;  with  these  free  silver  is  an 
absolute  necessity.  After  toning,  the  prints  should  be  invariably 
placed  in  a  bath  of  salt,  and  washed  in  one  or  two  changes 
of  water ;  this  prevents  any  further  toning  action,  and  a  whole 
batch  of  prints  may  be  toned  before  hypo  'is  touched  in  any 
shape  or  form.  It  is  absolutely  necessary  to  keep  the  toning 
bath,  dish,  or  fingers  uncontaminated  by  any  other  chemicals, 
or  spots  and  stains  will  be  the  result.  The  prints  should  be 
handled  as  little  as  possible  before  toning,  and  they  should  be 
kept  in  constant  motion  whilst  toning,  which  operation  should 
be  conducted  in  weak  daylight,  it  being  more  difficult  to  judge 
of  the  true  tone  by  artificial  light.  When  prints  are  given  a 
preliminary  bath  of  salt  and  water,  a  brilliant  brown  tone,  called 
"  Payne  Jenning's  Brown,"  results,  this  artist  invariably  using 
this  bath — a  preliminary  bath  of  carbonate  of  soda,  and  fuming 
the  paper  before  printing,  tending  to  give  purple  tones. 

Loss  of  Tone  in  Fixing.  This  is  so  often  a  complaint  that  no 
excuse  will  be  made  for  an  attempt  to  explain  this  annoying 
defect.  Some  baths  are  particularly  liable  to  it ;  and  some 
samples  of  gold,  which  the  author  has  tested  to  try  and  find  a 
reason  for  this  defect,  were  contaminated  with  chloride  of  copper, 
most  likely  an  accidental  adulterant  from  the  use  of  an  alloy  of 
gold  and  copper  'in  the  shape  of  scrap  gold,  old  jewellery,  or 
coins,  for  the  production  of  the  auric  salt.    If  copper  be  present, 

422 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ton 


part  of  the  image  would  be  toned  by  a  coloured  compound  of 
copper,  which  would  dissolve  in  the  hypo.  Many  years  ago  the 
addition  of  alkaline  gold  to  the  fixing  bath  was  recommended, 
and  the  author  has  proved  this  to  be  of  great  value  to  prevent 
loss  of  tone,  sel  d'or  being  actually  formed.  The  following  is 
the  formula  referred  to  : — 

Chloride  of  gold    I  gr.  or  -o6  grm. 

Carbonate  of  soda    20  grs.  ,,  1  -3  ,, 

Hypo    ...       ...    4  ozs.  ,,  124  grms. 

Water   20  „  ,,  500  c.cm. 

Add  the  gold  and  soda  mixed  together  to  the  hypo  solution, 
stirring  constantly.  Mr.  Anthony,  of  New  York,  recommends 
making  the  fixing  bath  distinctly  acid  both  to  test  paper  and 
sight  by  a  slight  turbidity,  by  the  addition  of  acetic  acid,  and 
then  neutralising  the  free  acid  by  the  addition  of  carbonate  of 
soda  or  liquor  ammonia  till  distinctly  alkaline  to  test  paper. 
This  the  author  has  tried  and  found  useful ;  but  in  every  case 
the  fixing  bath  should  be  distinctly  alkaline,  either  by  carbonate 
of  soda  or  ammonia. 

Yellowness  of  the  Whites  of  Prints.  This  is  at  once  a  sure 
sign  of  the  acidity  of  the  fixing  bath,  and  consequent  sulphur 
toning.  Nothing  can  be  done  but  to  immediately  destroy  the 
print,  and  make  the  fixing  bath  alkaline.  It  more  generally 
makes  its  appearance  in  cases  of  over-toning,  when  some 
secondary  action  seems  to  take  place. 

Black  Deposit  in  Toning  Baths.  On  keeping  for  some  time, 
especially  when  extreme  cleanliness  and  exclusion  of  actinic 
light  has  not  been  attended  to,  all  toning  baths  deposit,  more 
or  less,  a  purplish  black  precipitate,  which  is  metallic  gold  in 
an  extremely  fine  state  of  division  ;  and  when  this  deposit  has 
occurred  the  bath  is  utterly  useless.  To  renovate  these  old 
baths  the  following  plan  may  be  adopted  : — Collect  the  preci- 
pitate, wash  it  well,  and  shake  up  with  distilled  water  acidulated 
with  nitric  acid  (1  to  80);  add  to  this  a  solution  of  chloride  of 
lime,  made  by  mixing  80  grs.  of  chloride  of  lime  with  1  oz.  of 
water,  and  filtering ;  add  the  last  solution  gradually  to  the 
deposit  of  gold  mixed  with  water,  and  heat  to  the  boiling  point  ; 
it  will  then  be  found  that  as  more  chloride  of  lime  solution  is 
added  the  gold  will  dissolve.    When  entirely  dissolved,  it  may 

4*3 


Ton]  DICTIONARY  OF  PHOTOGRAPHY. 


be  kept  for  future  use,  and  sufficient  chalk  added  each  time  to 
neutralise  any  free  acid  before  using.  Another  method  of  pre- 
serving any  alkaline  toning  bath  is,  after  use,  to  add  sufficient 
hydrochloric  acid  to  make  the  bath  distinctly  acid  and  of  a 
yellow  colour.  When  required  for  use,  it  is  only  necessary  to 
add  sufficient  alkali  to  render  the  bath  colourless,  and  it  will 
work  as  well  as  a  fresh-made  one.  All  toning  baths  should  be 
distinctly  alkaline  ;  and  if  not  so,  alkali  should  be  added. 

All  amateurs  will  hail  with  welcome  a  bath  which  will  tone 
albumen  prints,  no  matter  how  long  they  have  been  printed,  or 
how  faded  and  yellow  they  may  be.  The  following  is  the  pro- 
cess invented  by  M.  Jaudaurek  of  Vienna,  which  is  of  great 
value  : — 

Solution  A. 

Distilled  water    17  ozs.  or  500  c.cm. 

Tungstate  of  soda   I54grs.  „   10  grms. 

Solution  B. 
Carbonate  of  lime  (chemical,  )  , 

pure)        ...       ...  I     6ogrs'  or  4§rms- 

Chloride  of  lime    15  ,,  „    1  grm. 

u       „    gold    60  „  „   4  grms. 

Distilled  water    15  ozs.  „  400  c.cm. 

This  solution  should  be  made  in  a  yellow  glass  bottle,  well 
shaken  and  allowed  to  stand  for  twenty-four  hours  :  then  filtered 
into  another  yellow  glass  bottle,  and  kept  well  stoppered.  When 
the  prints  have  been  washed,  they  should  be  placed  one  by  one 
is  the  following  toning  bath  : — 

Solution  A   5  ozs.  or  150  c.cm. 

,,       B   70-140  m.    „  4-8  „ 

They  should  not  tone  too  quickly ;  about  ten  minutes  in  summer 
should  be  the  shortest  time.  If  they  tone  quicker  than  this 
reduce  the  quantity  of  solution  B.  After  toning  wash  the  prints 
and  place  in  the — 

Fixing  Bath. 

Solution  A   5  ozs.  or  150  c.cm. 

Sodium  Hyposulphite       ...    230  grs.  „    15  grms. 
424 


DICTIONARY  OF  PHOTOGRAPHY. 


[Tra 


They  should  be  allowed  to  remain  in  this  till  the  yellow  colour 
has  quite  disappeared,  which  may  take  some  hours.  After  this 
has  disappeared  wash  in  the  usual  way. 

Tragacaiith(Ger.,  Tragant,  Tragantschlcim ;  Fr.,  Adragante ; 
Ital.,  Dragante).  A  gummy  exudation  from  the  stem  of  Astrag- 
alus verus,  collected  in  Asia  Minor.  It  should  be  nearly  white, 
and  sparingly  soluble  in  cold  water ;  more  so  in  hot ;  entirely 
soluble  in  alcohol. 

Transfers.  By  this  term  is  meant  the  pictures  produced  by 
transferring  an  image  developed  upon  a  temporary  support,  and 
affixed  afterwards  to  its  final  support.  These  are  usually  made 
by  the  carbon  or  collodion  process  ;  but  lately  a  special  trans- 
ferotype  paper  has  been  introduced,  which  gives  very  pleasing 
effects.  This  consists  of  a  film  of  insoluble  gelatino-bromide 
emulsion,  affixed  to  a  temporary  support  of  paper  by  a  soluble 
substratum.  The  method  of  exposure  and  after-treatment  is 
precisely  the  same  as  for  bromide  paper,  but  they  can  be  toned 
after  transfer  by  the  following  process  : — 

Solution  A. 

Ferricyanide  of  potash  ...  100  grs.  or  6  grms. 
Distilled  water    24  ozs.  ,,  700  c.cm. 

Solution  B. 

Uranic  nitrate   100  grs.   or    6  grms. 

Distilled  water        ...       ...    24  ozs.  „  700  c.cm. 

Keep  these  separate,  and  mix  only  for  immediate  use.  Take 
equal  parts  of  A  and  B,  mix,  and  immerse  the  transferred  picture 
in  the  bath  till  the  desired  tone  is  obtained.    Fix  again  in 

Hyposulphite  of  soda  ...  3  ozs.  or  90  grms. 
Water    16    ,,     „  470  c.cm. 

The  darker  the  print  the  deeper  the  tone.  As  this  process 
intensifies  (it  is  practically  nothing  but  uranium  intensification) 
medium  light  prints  give  the  best  results.  The  above  formula 
gives  warm  red  tones ;  for  rich  browns,  leave  the  prints  in 
toning  solution  till  they  begin  to  turn  ;  then  immerse  in  weak 
alum  solution,  wash,  and  fix.    To  transfer  these,  lay  the  wet 

425 


Tra] 


DICTIONARY  OF  PHOTOGRAPHY. 


print  upon  the  surface  to  which  it  is  to  be  transferred,  which 
may  be  either  polished  or  ground  opal  glass,  clear  or  ground 
glass,  porcelain,  wood,  ivory,  canvas,  or  any  other  material 
which  will  stand  hot  water.  The  surface  must  be  perfectly  free 
from  grease  or  dirt ;  squeegee  the  wet  print  carefully  on  to  it, 
and  put  under  a  weight  and  blotting  paper  to  dry.  When  dry 
pour  hot  water  at  about  1600  F.  upon  the  paper  till  it  begins 
to  blister  ;  then  raise  one  corner  carefully  with  a  knife,  and  strip 
the  paper  off,  and  gently  rub  the  picture  with  a  wet  pad  of 
cotton-wool.  The  paper  may  be  stripped  any  time  after  the 
picture  has  been  on  its  support  thirty  minutes,  but  it  is  better 
to  let  it  dry.  Lantern  slides,  plaques,  tiles,  and  lamp  shades 
may  all  be  ornamented  in  this  manner. 

Translucent.   See  Light. 

Transparent.   See  Light. 

Under-Exposure  is  when  the  duration  of  exposure  of  the 
sensitive  surface  is  not  sufficiently  prolonged  to  impress  the 
details  of  the  object  on  the  sensitive  surface.  Its  effects  are 
thinness  of  negative,  without  detail.  When  under-exposure  is 
suspected,  the  only  thing  to  do  is  to  reduce  the  bromide  in  the 
developer,  and  coax  the  image  out  with  very  slow  and  careful 
development.  To  increase  density,  intensification  may  be  re 
sorted  to,  but  nothing  can  improve  the  lack  of  detail. 

Uranium  (Ger.,  Uran;¥v.}  Urane  ;  Ital.,  Uranio).  U  =  240. 
A  rare  metal  never  found  in  a  pure  state,  but  as  an  impure 
oxide,  called  pitchblende.  It  is  used  in  the  form  of  nitrates  for 
preparing  a  printing-out  paper,  and  for  intensification. 

Uranium  Chloride  (Ger.,  Uraniumchlorid ;  Fr.,  Chlorure 
d'uranium:  Ital.,  Cloruro  di  uranio).  U02C12H20  =  361.  Very 
soluble  in  alcohol  and  water.  It  has  been  used  for  toning  and 
as  a  sensitive  salt  for  a  platino-uranotype  process  {g.v.\ 

Uranium  Nitrate  (Ger.,  Uranylnitrat,  Salfietersatires 
Uranoxyd ;  Fr.,  Azotate  d'urane,  Nitrate  d'urane ;  Ital.,  Azotato 
di  uranio).  Uranic  nitrate  is  prepared  by  digesting  pitchblende 
in  hydrochloric  acid,  to  dissolve  out  the  other  metals,  then 
roasted  with  charcoal  twice,  and  the  residue  dissolved  in  nitric 
acid,  and  purified  by  crystallisation.     U02(N03)2,6H20  =  314. 

426 


DICTIONARY  OF  PHOTOGRAPHY. 


[Ura 


This  is  a  brilliant  yellowish-green  crystalline  salt,  very  deliques- 
cent. Solubility  215  per  cent,  in  cold  water,  33*3  per  cent,  in 
alcohol,  and  25  per  cent,  in  ether.  It  is  decomposed  by  light 
when  in  contact  with  organic  matter  into  a  uranous  nitrate. 

Uranium  Printing.  The  colours  obtained  by  the  use  of 
uranium  salts  are  decidedly  pleasing,  tending  to  a  terra-cotta  or 
copper  colour,  which  may  be  varied  at  will.  The  sensitising 
solution  may  be  prepared  as  follows  : — 

Uranium  nitrate    80  grs.  or   5  grins. 

Distilled  water    1  oz.    ,,30  c.cm. 

Preserve  in  the  dark.  The  papers  may  be  floated  on  this  for 
five  minutes,  or  the  solution  may  be  applied  with  a  brush  or  tuft 
of  cotton  wool.    The  following  may  also  be  used : — 

Uranium  nitrate  ...  ...  80  grs.  or    3  grms. 

Mercuric  nitrate  ...  ...  20   ,,  ,,     l'2  ,, 

Distilled  water    1  oz.  ,,  30  c.cm. 

Or 

Uranium  nitrate  ...  ...  80  grs.  5  grms. 

Cupric  nitrate  or  sulphate  ...  20  „  1-2  „ 

Distilled  water  ...  ...      1  oz.  ,,     30  c.cm. 

The  papers  should  be  exposed  under  a  negative  in  sunlight  until 
all  the  principal  detail  is  visible,  and  then  floated  on  a  developer 
till  the  tone  desired  is  obtained. 

Potassium  ferridcyanide...       ...    50  grs.  or    1  grm. 

Distilled  water    1  oz.  ,,   100  c.cm. 

This  will  give  a  reddish-brown  tint. 

Silver  nitrate    25  grs.  or    1  grm. 

Distilled  water    ...    1  oz.  „  200  c.cm. 

This  will  give  a  greyish  image,  which  can  be  toned  after  washing 
in  a  combined  toning  and  fixing  bath. 

Chloride  of  gold   1  gr.  or    1  grm. 

Distilled  water    1  oz.  „  500  c.cm. 

This  should  be  brushed  over  the  image,  and  gives  a  purplish- 

427 


Ura] 


DICTIONARY  OF  PHOTOGRAPHY. 


black.  The  prints  after  development  should  be  washed  in  a 
bath  of  hydrochloric  acid,  I  to  80,  and  then  again  washed 
thoroughly. 

Uranium  Toning.    See  Bromide  Paper  and  Platinotype. 
U.S.  or  Uniform  System.   See  Diaphragms. 

Varnish.  A  solution  of  resinous  bodies  in  a  volatile  solvent, 
used  for  covering  the  film  of  a  negative  with  a  coating  of  matter 
impermeable  to  air  and  damp. 

The  following  is  a  table  of  the  principal  varnishes  of 
commerce  : — 


I.  Copal,  for  fine  paintings. 
2  Japanners'  copal. 

3.  Best  body. 

4.  Carriage. 

5.  Best  white  hard. 

6.  Best   white  hard,  for 

violins. 


7.  Best  brown  hard. 

8.  Turpentine. 

9.  Crystal. 

10.  Amber. 

11.  Paper. 

12.  Sealing-wax. 

13.  Black. 


Ingredients. 

1 

2 

3 

4 

« 

6 

7 

8 

9 

10 

11 

12 

13 

Shellac   lbs. 

Mastic    „ 

Sandarac      ...  „ 

Dammar   „ 

Resin    „ 

Amber    „ 

Benzoin   „ 

Copal      ...     .;.  ,, 
Sp.  of  wine  ...gals. 
Turpentine,  oil 

of    „ 

Linseed,  oil  of  ,, 
Turpentine    ...  lbs. 
do.  varnish  ...  pts. 
do.  Venice  ...  ozs. 
Powdered 

glass  lbs. 

Black  sealing- 
wax    „ 

Red  do   „ 

2 
1 
4 

2 

1  •> 

I 

2 

4 

4 

'6 

1 

1 

8 

3 
2 

7 

3 

1 
2 

8 

3h 
2 

8 
Sh 

1 

5 

1 

1 

4 
2 

1 

I 

2 

18 

18 

4 

3 

l\ 

428 


DICTIONARY  OF  PHOTOGRAPHY.  [Var 

For  photographic  purposes  special  varnishes  are  required,  and 
the  following  will  be  found  very  good  ones  : — 

Negative  Varnish 
(0 

Orange  shellac    i£  oz.  or   38  grms. 

Mastic    J  11  11     7  11 

Sandarac   i|  ,,        38  „ 

Oil  of  turpentine   £  7  ,, 

Venice  turpentine    \  ,,         7  " 

Camphor   10  grs. o*6  grm. 

Methylated  spirit,  66  over  proof  .  20  ozs.  „  500  c.cm. 

Or 

(2) 

Orange  shellac    2  ozs.  or  60  grms. 

Sandarac  ...       ...        ..       ...  2        „  60 

Canada  balsam    ...       ...       ...  60  grs.  ,,     4  ,, 

Oil  of  lavender    ...       ...       ...  1  oz.        25  c.cm. 

Methylated  spirit...       ...       ...  16  ozs.  „  400 

Or 

(3) 

White  hard  varnish       ...       ...  15  ozs.  or  400  c.cm. 

Methylated  spirit   25         ,,  700 

The  above  varnishes  must  be  flowed  over  the  negative,  and  then 
dried  before  a  brisk  fire.  The  following  may  be  applied  without 
warming : — 

(4) 

Negative  varnish   ...      5  ozs.  or  150  c.cm. 

Liq.  ammonia  *88o    Add  sufficient  to  cause 

the  cloudiness  first 
formed  to  disappear. 


Or 


White  hard  varnish       ...       ...  10  ozs.  or  250  c.cm. 

Liq.  ammonia  880    As  above. 

Water    5  ozs.  or  125  c.cm. 

420 


Var] 


DICTIONARY  OF  PHOTOGRAPHY. 


Burton  has  strongly  recommended  the  following : — 

Sandarac   I  lb. 

Venice  turpentine    4  fluid  ozs. 

Oil  of  turpentine   8    „  ,, 

Alcohol  (sp.  gr.  -825)    1  gallon. 

The  alcohol  should  be  poured  over  the  gum,  which  will  dissolve 
in  a  few  hours  without  heat,  if  the  vessel  be  occasionally  shaken- 
The  Venice  turpentine  is  then  added,  and  the  measure  rinsed 
out  with  the  oil  of  turpentine,  which  is  also  added.  The  varnish 
is  then  ready  for  use. 

Black  Varnish. 

Benzine   1000  parts. 

India-rubber       ...       ...       ...       6  „ 

Asphalt   ,       ...    300  ,, 

Lamp  black   Quant,  suff. 

Matt  Varnish. 
This  can  be  prepared  from  : — 
(1) 

Sandarac   100  parts. 

Mastic  (in  tears)   20  ,, 

Ether   1000  „ 

Benzine    500 

(2) 

Sandarac   60  „ 

Gum  Dammar    60  „ 

Ether   1000  „ 

Benzine   350  to  400  parts. 

The  more  benzine  is  added  the  coarser  the  grain,  and  vice  versa. 
Lainer  strongly  recommends  : — 

Ether    100  c.cm. 

Sandarac   10  grms. 

Dissolve  by  agitation,  fllte*,  and  add — 

Toluol    35  to  40  c.cm 

43° 


DICTIONARY  OF  PHOTOGRAPHY. 


[Vie 


View  Finder.  This  is  a  little  instrument  used  for  instan- 
taneous photography  to  see  when  the  moving  object  is  in  the 
middle  of  the  field  of  view  and  in  the  middle  of  the  plate.  One 
form  is  a  piano  or  double-concave  lens  mounted  on  the  front  of 
the  camera,  the  eye  being  placed  at  the  back  of  the  camera.  A 
good  form  of  this  finder  is  with  a  concave  lens  mounted  with  a 
mirror  at  an  angle  of  45°  behind  it.  Another  good  method  is  to 
utilise  the  camera  obscura,  which  may  be  made  at  a  trifling  cost 
out  of  a  spectacle  double-convex  lens  of  about  1^  to  2-in.  focus 
mounted  in  a  brass  tube,  a  mirror  at  an  angle  of  45 °,  and  a  piece 
of  ground  glass  on  the  top  with  a  shade.    In  the  accompanying 


Fig.  97. 


diagram  showing  the  arrangement,  A  B  c  D  is  a  rectangular  box  of 
card  or  wood,  L  a  lens  in  the  mirror,  g  the  ground  glass,  s 
movable  shade,  which  can  be  raised.or  lowered  at  will.  Another 
method  is  to  use  the  focussing  screen,  which,  when  turned  back 
over  the  top  of  the  camera,  should  have  lines  drawn  on  it  as 
shown  in  the  diagram  ;  then,  when  the  eye  is  placed  at  A,  and 
looking  along  ab,  the  object,  when  opposite  this,  will  be  in 
the  centre  of  the  plate.  Or  a  double-convex  lens  of  exactly 
the  same  focus  as  the  photographic  lens  may  be  mounted 
on  the  front  of  the  camera,  and  the  focussing  cloth  thrown 
over  the  whole  so  as  to  form  a  second  or  temporary 
camera. 

View  Meter.  An  instrument  used  to  gauge  the  amount  of 
view  included  by  the  lens  upon  the  focussing  screen  without 
the  trouble  of  setting  up  the  camera.    The  following,  which  has 

431 


Vie]  DICTIONARY  OF  PHOTOGRAPHY. 

now  been  placed  upon  the  market  commercially,  is  a  very  good 
form : — 

abcd,  a  brass  tube  bearing  at  one  end  a  cap  in  which  is  an 
opening  (g  h),  bearing  a  proportionate  size  to  the  plate  used  : 
for  instance,  for  quarter-plates,  or  4^  by  3^,  the  opening  may  be 


Fig,  98. 


H  in-  by  yf ;  or  for  half-plate,  f|  by  This  opening  frames 
the  view,  and  limits  its  extent  according  to  the  distance  the 
inner  tube  is  drawn  out.  e  f  is  a  double  concave  lens  of  i^-in. 
focus,  and  m  a  double  convex  lens  of  3-in.  focus ;  when  the  eye 
is  applied  to  the  convex  lens  the  picture  is  viewed  in  miniature, 
p  will  show  front  view  of  cap. 


Fig.  99. 


To  use  this  it  must  be  adjusted  to  the  lenses  with  which  it 
will  be  worked.  To  do  this  it  is  only  necessary  to  erect  the 
camera,  focus  carefully,  and,  marking  two  prominent  objects  on 
the  edges  of  the  screen,  adjust  the  small  view-meter  till  the 
same  objects  are  exactly  on  the  edges  of  the  field  of  view  in 
that.    Now  mark  on  the  inner  sliding  tube  with  a  knife  or  file 

432 


DICTIONARY  OF  PHOTOGRAPHY. 


[Was 


the  exact  point  to  which  it  was  pulled  out  or  in,  and  this  will 
always  include  the  amount  of  view  included  by  that  lens.  By 
fastening  two  fine  wires  across  the  cap  p,  as  shown  by  the 
dotted  lines,  it  will  serve  well  also  as  a  view-finder,  as,  when 
the  moving  object  is  at  the  point  of  intersection  of  the  crossed 
wires,  it  will  be  in  the  centre  of  the  plate.  It  may  also  be  used 
as  some  guide  to  the  probable  exposure  by  placing  inside  the 
cap  a  circle  of  blue  glass,  so  as  to  cut  off  all  the  rays  but  those 
chemically  active  and  which  affect  the  plate. 

Vignetting.  This  consists  of  shading  off  the  margins  of 
a  picture,  so  as  to  cause  the  figure  or  subject  to  gradually  fade 
away.  There  are  numerous  methods  of  effecting  this  :  one  is  by 
the  use  of  glass  with  oval  or  other  shaped  openings  surrounded 
by  a  gradually  deepening  margin  of  coloured  non-actinic  glass. 
These,  however,  are  not  satisfactory.  Another  method  is  that 
employed  by  the  French  operators  of  using  graduated  thicknesses 
of  tissue  paper  with  serrated  edges.  Another  method  is  to  use 
wooden  covers  with  openings  having  the  underneath  edges 
bevelled  off.  But  the  best  of  all  is  to  use  stout  sheet  lead  or 
pure  tinfoil,  and  to  cut  the  sized  opening  required,  and  either  to 
slightly  turn  up  the  edges  or  serrate  them,  so  as  to  soften  the 
outline ;  and  the  farther  the  vignetting  shape  is  placed  from 
the  negative  the  larger  the  vignette  and  the  softer  the  outline. 
When  the  so-called  Russian  vignettes  or  images  on  a  black 
ground  are  required,  a  very  good  method  is  to  use  a  vignetter  in 
front  of  the  lens  or  between  the  lens  and  the  plate.  When 
used  in  front  of  the  lens  a  card  or  metal  plate  with  the  particular 
shaped  opening  is  supported  in  front  of  the  lens,  and  gently 
moved  backwards  and  forwards  an  inch  or  two  during  exposure. 
The  distance  in  front  of  the  lens  being  found  by  adjustment. 
When  used  in  the  camera  the  most  convenient  form  is  that  of  an 
American  invention  which  is  practically  a  large  iris  diaphragm 
placed  about  a  third  of  the  focus  from  the  lens.  Obviously  cards 
or  metal  plates  may  be  used  in  the  same  way. 

Washing  Negatives  and  Prints.  — Upon  the  perfection  of  the 
washing  process  practically  depends  the  life  of  negatives  and 
prints,  as  the  presence  of  hyposulphite  of  soda,  or  silver,  tends  to 
fading  of  negatives  and  prints,  and  yellowness  of  the  whites  of  the 
latter.     There  are  numerous  commercial  washing   tanks  and 

433  FF 


Was] 


DICTIONARY  OF  PHOTOGRAPHY. 


troughs,  which  answer  their  purpose  admirably.  Running  water 
is  the  most  effective  means  for  the  elimination  of  the  undesirable 
faults,  but  when  the  water  supply  is  limited,  the  prints  or  nega- 
tives should  be  allowed  to  soak  in  water  for  ten  minutes,  and 
then  the  water  changed ;  and  this  operation  repeated  six  times 
will  usually  be  sufficient  for  negatives  and  prints.  Messrs. 
Grundy  &  Haddon  have  proved  that  ten  minutes  thorough  wash- 
ing is  quite  sufficient  to  eliminate  all  the  hyposulphites  that  can 
be  eliminated,  and  it  is  a  recognised  fact  that  prolonged  soaking 
of  prints  in  water  is  one  of  the  best  means  of  obtaining  faded  and 
spoilt  prints. 

Wastes.    See  Residues. 

Waxing  Negatives.    See  Oiling. 

Weights  and  Measnres.  The  confusion  which  reigns  in 
the  photographic  world  with  regard  to  weights  and  measures  is 
something  appalling.  Numerous  plans  have  been  proposed  to 
remedy  this,  but  at  present  with  little  effect ;  the  confusion  arises 
in  great  measure  from  the  numerous  systems  of  weights  and 
measures  used  in  different  countries.  All  solid  chemicals  are 
sold  by  avoirdupois  weight,  whilst  many  formulae  are  written  in 
what  is  called  apothecaries'  weight.  It  has  been  proposed  to  use 
the  metric  system,  but  at  present  there  seems  no  likelihood  of  its 
coming  into  general  use.  The  author  has  endeavoured  through- 
out the  Dictionary  to  give  all  formulae  in  standard  weights  about 
which  there  can  be  no  dispute.  As  a  standard  for  dry  substances 
the  grain  has  been  employed,  and  for  liquids  the  minim,  or  the 
ounce  of  480  minims,  except  in  some  cases  where  the  weights  are 
practically  immaterial,  where  a  few  grains  more  or  less  would 
make  no  appreciable  difference.  The  author  does  not  intend  to 
enter  into  any  arguments  on  the  question,  but  simply  gives  those 
tables  of  weights  in  general  use. 


Apothecaries'  Weight. 


20  grains 
3  scruples  . . . 
8  drachms... 


1  scruple  (3). 
1  drachm  (5). 
1  ounce  (5). 


The  above  weights  are  used  by  chemists  for  the  compounding  of 
prescriptions, 

434 


DICTIONARY  OF  PHOTOGRAPHY 


[Wei 


i  oz.  (3j)  ==  8  drms.  (5viij)  =  24  scruples  (3xxiv)  =  480  grs. 
(The  pound  in  this  weight  is  never  used;  it  contains  12  ozs.  == 
5,760  grs.) 


Avoirdupois  Weight. 


16  drachms ... 
16  ounces  ... 


ounce, 
pound. 


1  lb.  =  16  ozs.  =  256  drms.  =  7,000  grs.  (This  weight  is  used 
by  all  dealers  for  retailing  chemicals,  etc.    1  oz.  =  437*5  grs.j. 


Liquid  Measure. 


60  minims 
8  drachms 

20  ounces 
8  pints 


1  drachm  (f.  5). 
1  ounce  (f.  3). 
1  pint  (O). 
1  gallon  (C). 


1  gal.  (Cj)  =  8  pts.  (Oviij)  =  160  ozs.  (f.  5,  160)  =  1,210  drms. 
(f.  5»  1,280)  =  76,000  minims. 

The  following  is  the  Metric  System  of  weights  and  measures 
in  use  in  France  and  on  the  Continent  generally,  and  in  the 
United  States,  and  in  England  amongst  scientific  chemists.  The 
division  in  each  case  is  by  10,  so  that  it  is  extremely  easy  to 
calculate  the  division  or  multiplies  of  any  weight. 


Lineal  Measure. 


1,000  millimetres 
100  centimetres 
10  decimetres 
10  metres 
100  „ 
1,000  ,, 


1  metre. 
I  n 

I  M 

I  decametre. 
1  hectometre. 
1  kilometre. 


The  metre  is  the  unit,  and  is  equal  to  39*37  English  inches 
Liquid  Measure. 


1,000  millilitres 
100  centilitres 
10  decilitres 
10  litres 
100  ,, 
1,000  „ 


1  litre. 
I  „ 

I  M 

I  decalitre. 

1  hectolitre 

1  kilolitre, 


345 


Wei]  DICTIONARY  OF  PHOTOGRAPHY. 

The  litre  is  the  unit,  and  is  equal  to  35*216  fluid  ozs.  Liquid 
measures  are  usually  expressed,  however,  as  cubic  centimetres, 
or  c.cm. ;  ='i6*8  minims. 

Dry  Measure. 
1,000  milligrammes         ...       =       1  gramme. 
100  centigrammes         ...       =  1 
10  decigrammes  ...       =  1 

10  grammes      ...       ...       =      ,  1  decagramme. 

100       „  ...       ...       =       1  hectogramme. 

1,000      ,,    =3       1  kilogramme. 

The  gramme  is  the  unit,  and  is  equal  to  15*432  grs. 

For  converting  these  weights  into  English,  the  following  tables 
will  be  found  sufficiently  accurate  for  all  purposes  : — 

Conversion  of  Grammes  into  Grains. 

1  gramme   =       13*432  grains. 

2  grammes...       ...       ...       ==       30-864  ,, 

3  h    =       46*926  „ 

4    =       61-628  „ 

5  »    =       77'i6o  „ 

6  „    =       92-592  ,, 

7    ==     108*024  ,, 

8  „    ==     123-466  „ 

9  rt       -   =     138*898  „ 

Conversion  of  Grains  into  Grammes. 

1  grain    =         -0648  gramme. 

2  grains    =         -1296  ., 

3  >.    =  '1944 

4    =  -2592 

5  »   ==  -3240 

6  „        ...    m  -3888  „ 

7  „    =  -4536 

8  ,   =  -5184  „ 

9    =  -5832 

Supposing  it  is  desired  to  convert  506*94  grammes  into  grains, 
the  table  is  used  as  follows : —  » 

436 


DICTIONARY  OF  PHOTOGRAPHY. 


[Wei 


500    grammes    =  77160  grains. 

6        ,   =  92592 

•90  gramme    =  1 3*889 

•04      *    =  *6l7  „ 

7823-098  „ 

The  numbers  taken  from  the  tables  simply  require  the  altering 
of  the  position  of  the  decimal  point. 

The  following  may  be  useful  for  those  short  of  weights  to 
obtain  an  approximate  weight : — 

Weight. 

1  sovereign,  new  .. .       ...       ...    123-274  grains. 

1  shilling  ...       ...       ...       ...  87.273 

48  pennies  ...       ...       ...       ...       1  lb.  avoirdupois. 

1  halfpenny  and  1  threepenny-piece  \  ounce. 
1  florin  and  1  sixpence   \  ounce. 

3  pennies    1  ,, 

4  half-crowns  and  1  shilling     ...       2  ounces. 
4  florins,  1  half-crown,  2  pennies       4  ,, 

It  has  become  somewhat  general  lately  to  give  formulae  in 
parts,  and  this  is,  though  not  strictly  accurate,,  a  somewhat  con- 
venient method  of  translating  metric  measures  into  English 
weight  and  measures.  If  in  every  case  the  grain  is  taken  as  the 
unit,  no  confusion  can  arise. 

Frequently  we  find  a  solution  spoken  of  as  "  a  48-grain  bath,'' 
"  a  60-grain  bath,"  etc.  ;  and  this  means  that  each  ounce  of  the 
solution  contains  48  or  60  grains  of  the  salt. 

Ten  par  cent,  solutions  are,  again,  somewhat  of  a  trouble  to 
some,  and  the  trouble  arises  from  the  fact  that  we  are  in  the 
habit  of  measuring  liquids,  and  that  the  avoirdupois  ounce  con- 
tains only  437'5  grains,  whilst  a  fluid  ounce  contains  480  minims. 
To  make  a  10  per  cent,  solution  of  any  salt  we  proceed  as 
follows  : — Let  us  take,  for  instance,  an  ounce  of  pyro.,  and  it  is 
required  to  make  a  10  per  cent,  solution  ;  that  is  to  say,  we 
require  a  solution,  every  10  minims  of  which  shall  represent 
1  grain  of  pyro. ;  then,  having  437*5  grains  of  pyro.,  the  total 
bulk  of  the  solution  will  be  437  5  x  10  =  4375  minims  =  9  oz. 

437 


Wet] 


DICTIONARY  OF  PHOTOGRAPHY. 


55  minims.  Any  other  strength  solution  may  be  made  in  the 
same  way. 

Wet  Collodion  Process.  This  was  the  first  process  in  which  a 
vehicle  for  the  sensitive  silver  salt  was  used.  Either  negatives  or 
positives  can  be  produced  ;  and  the  latter,  when  taken  upon  thin 
enamelled-iron  plates,  are  known  as  ferrotypes  or  tintypes.  The 
following  is  a  short  resume  of  the  process  : — A  well-cleaned  glass 
plate  is  coated  with  Collodion  (q.v.),  and  as  soon  as  the  collodion 
has  set,  this  coated  plate  is  immersed  in  a  bath  made  as  follows : — 

Nitrate  of  silver   ...       ...       ...    119  grs.    or     7  grms. 

Potassium  iodide   1  gr.      , ,   *o6  grm. 

Distilled  water     ...       ...       ...       8  ozs.    ,,  200  c.cm. 

Dissolve  the  silver  salt  in  2  oz.  of  water,  and  the  potash  in  \  oz. 
Add  the  latter  to  the  former,  and  add  the  remainder  of  the  water. 
Filter,  and  test  for  acidity.  If  the  blue  litmus  paper  is  not  turned 
red  after  an  immersion  of  some  short  period,  a  few  drops  of  a 
dilute  nitric  acid  (1  in  12)  should  be  added  till  the  bath  is 
decidedly  acid.  The  plate  is  exposed  whilst  still  wet,  the 
exposure  being  about  ten  times  that  for  gelatine  dry  plates  of 
ordinary  rapidity  under  similar  circumstances.  For  development 
any  of  the  following  may  be  used,  but  the  author  prefers  Nos. 
2,  3,  and  4,  the  last  being  especially  useful,  as  shorter  exposure 
is  required,  and  more  detail  is  brought  out.  With  No.  5  longer 
exposure  is  required,  but  extreme  contrast  is  obtained  : — 


No.  1. 


Ferrous  sulphate 

  3°°  g^. 

or   20  grms 

Glacial  acetic  acid 

...    200  mins. 

„    12  c.cm. 

Methylated  spirit 

  i  oz. 

„    12  „ 

Distilled  water  ... 

  10  ozs. 

M     250  „ 

No.  2. 

Ferrous  sulphate 

  200  grs. 

or   12  grms. 

Cupric 

  100  „ 

if     6  „ 

Glacial  acetic  acid 

  200  mins. 

„    12  c.cm. 

Methylated  spirit 

  ^  oz. 

»    12  „ 

Distilled  water  ... 

  10  ozs. 

M     250  ,, 

438 


DICTIONARY  OF  PHOTOGRAPHY. 


[Wet 


No.  3. 


Ferrous  sulphate 

Cupric   

Distilled  water  .. 


240  grs. 

30  M 
5  oz. 


or   15  grms. 

2  „ 
125  c.cm. 


Nitrate  of  baryta 
Glacial  acetic  acid 
Methylated  spirit 
Distilled  water  ... 


30  grs.  or  2  grms. 
2  drms.         6  c.cm. 

£oz.      „  12  5  „ 

5  ozs.    ,,  125 


Dissolve  A  and  B  separately,  then  mix  and  filter. 


No.  4. 

Ferrous  sulphate 

Glacial  acetic  acid   

Formic  acid  (sp.  gr.  1  -060 ) 

Methylated  spirit   

Distilled  water  


Ferrous  sulphate 
Glacial  acetic  acid 
Lump  sugar 
Methylated  spirit 
Distilled  water  ... 


No.  5. 


300  grs. 
200  mins. 
100  „ 
240  „ 
10  ozs. 


200  grs. 
180  mins. 
100  grs. 
240  mins. 
10  ozs. 


or  20  grms. 
„  12  c.cm. 
n     6  „ 

M  1  *  It 

M  „ 

or    12  9  grms. 

10  8  c.cm. 
,,      6-5  grms. 

147  c.cm. 

M     2957  M 


No.  6. 

Ammonio-sulphate  of  iron 

Glacial  acetic  acid   

Methylated  spirit 
Distilled  water  ... 


.    250  grs.    or  10  grms. 

.    250  mins.  ,,  15  c.cm. 

.    240    „  12  5  „ 

10  ozs.    ,,  250  ,, 

To  develop  the  exposed  plate  is  should  be  fixed  upon  a  pneumatic 
holder  and  a  little  of  the  developer  poured  evenly  on  to  the 
surface,  and  gently  rocked  bockwards  and  forwards  till  the  image 
is  sufficiently  developed,  when  it  may  be  poured  off.  The  image 
nearly  always  requires  intensification  for  negative  work,  and  the 
following  may  be  used  : — 

Ferrous  sulphate         ...       ...     5  grs.  or 

Citric  acid    10  „  „ 

Distilled  water   1  oz.  „  25 

439 


0  3  grm. 
o-6  „ 


Wid] 


DICTIONARY  OF  PHOTOGRAPHY. 


Add  immediately  before  using  a  few  drops  of 

Silver  nitrate    10  grs.  or  o*6  grm. 

Distilled  water   i  oz.  „  25  c.cm. 

Pour  on  to  the  unfixed  negative,  and  rock  backwards  and  for- 
wards till  dense  enough.    Then  fix  in 

Potassium  cyanide    120  grs.  or     7-5  grms. 

Distilled  water   10  ozs.  „  250  c.cm. 

Wash  thoroughly,  dry,  and  varnish. 

Wide-Angle  Lens.   See  Lens. 

Woodburytype.  This  is  a  very  beautiful  photo-mechanical 
process,  and  consists  of  exposing  a  thick  film  of  bichromated 
gelatine  to  light  under  a  negative ;  and  when  fully  exposed  it  is 
washed  to  dissolve  the  unacted-upon  soluble  portions,  and  after 
being  soaked  in  alum  is  dried.  When  dry,  the  gelatine  print, 
which  at  this  period  looks  like  a  delicate  piece  of  silk  with  the  ■ 
image  in  relief,  is  placed  on  to  a  bed  of  metal,  and  a  pressure  of 
from  four  hundred  to  five  hundred  tons  brought  to  bear  on  it. 
This  forces  the  gelatine  into  the  metal,  and  makes  an  impression 
the  same  as  a  seal  on  hot  sealing  wax,  the  film  of  gelatine  itself 
being  unharmed  and  used  over  and  over  again.  The  metal  sheet 
bearing  an  impression  now  becomes  a  mould,  and  this  is  placed 
in  a  press,  and  some  special  liquid  gelatine  ink  is  poured  on  to 
it,  and  a  sheet  of  non-absorbent  paper  placed  over.  The  press 
is  now  closed,  and  pressure  being  applied,  it  is  obvious  that  the 
ink  will  leave  the  high-lights  and.  collect  in  the  shadows.  When 
the  gelatine  ink  has  set,  the  paper  is  removed,  bearing  the  image, 
and  is  fixed  in  alum  and  dried. 

Siannotype.  This  is  also  an  invention  of  Mr.  Woodbury,  and 
in  this  process  an  image  in  intaglio  is  produced  by  exposure  of 
a  bichromated  gelatine  film  under  a  positive,  and  this  is  coated 
with  tinfoil,  and  used  for  printing  from  in  almost  the  same 
manner  as  in  Woodburytype. 

Yellow  Fog.   See  Fog. 

Yellowness  of  Prints.   See  Toning. 

Yellow  Stain.   See  Clearing  Bath. 

Zinc  (Ger.,  Zink  ;  Ft.,  Zinc;  Ital.,  Zincd).   Zn  =  65  exists  as 
440 


DICTIONARY  OF  PHOTOGRAPHY. 


[Zin 


calamine  or  carbonate,  as  sulphide  in  zincblende,  as  oxide,  and 
occasionally  in  a  pure  state.  It  is  used  in  photography  in  several 
photomechanical  processes,  and  its  salts,  the  bromide,  iodide, 
and  chloride,  which  are  formed  in  somewhat  similar  manner  to 
the  cadmium  salts,  are  not  much  used.  Zinc  hypochlorite  has 
lately  been  recommended  for  making  hypo  eliminator.  The 
formulae  for  the  salts  of  zinc  are — Bromide,  ZnBr,  =  225  ;  Iodide, 
ZnL  =  319  ;  Chloride,  ZnCl2  =136  ;  Hypochlorite,  ZnCL  ZnCl202 
=  304. 

Zincography.  A  photo-mechanical  printing  process,  in  which 
the  image  is  impressed  upon  a  zinc  plate  by  means  of  a  greasy 
ink,  and  an  etching  fluid  being  applied  which  eats  away  the 
groundwork,  leaving  the  image  in  relief,  so  that  it  can  be  printed 
from  like  ordinary  type. 


441 


APPENDIX. 


I.  PLATE-MAKERS'  FORMULA. 

In  this  section  is  included  the  formulce  and  working  directions  for  all, 
or  nearly  all,  of  the  commercial  varieties  of  plates  and  papers. 

Blair's  Film.  Mix  each  solution  in  the  order  given.  Use 
equal  parts  of  each.    Keep  the  developer  cool  by  using  ice. 

Amidol  Developer  Formula. 

Water  ...       ...    ...       ...       ...     24  ozs. 

Sulphite  Soda  (Crys.)    2  „ 

Amidol  120  grs. 

Hydrochinone   ...       ...       ...       ...  60 

Eikonogen       ...       ...       ...       ...       ...       ...      60  „ 

Bromide  of  potassium  ...       ...       ...       ...      12  „ 

Mix  in  order  named ;  use  3  parts  of  this  solution  to  2  parts 
water.  As  soon  as  developed,  rinse  in  clear  water  to  remove  the 
developer  and  transfer  to  the  fixing  bath. 

Water   I  qt. 

Hypo   fib. 

After  fixing,  wash  one  hour  in  running  water  or  by  changing  the 
water  in  tray,  and  then  soak  for  half  an  hour  in  a  soaking  solution 
composed  of — 

Alcohol    4  ozs. 

Water   16  „ 

Glycerine        ...       ...       ...       ...       ...       ...         \.  „ 

Do  not  rinse  the  film  after  removing  from  the  soaking  solution. 
The  object  of  the  soaking  solution  is  to  prevent  the  film  from 
curling  when  dry. 

To  Dry.  Pin  the  film  by  the  corners  to  a  board  and,  when 
thoroughly  dry,  wipe  off  the  back  with  a  soft  cloth.  It  is  of  the 
utmost  importance  to  keep  the  finished  film  flat,  do  not  roll  it  up 
as  it  causes  trouble  in  printing.  Any  ordinary  pyro-soda  de- 
veloper may  also  be  used  with  good  results  for  these  films. 

442 


I.     PLATE-MAKERS*  FORMULAS. 


"Cadett"  Plates. — "Ordinary"  "  Lightning"  and  "Snap- 
Shotr 

Stock  Solution. 

Pyrogallic  acid          ...                             ...        ...  I    oz.  av. 

Ammonium  bromide  ...       ...       ...        ...       ...  }  „ 

Potass  metabisulphite          ...   I  „ 

Distilled  water  to  make  altogether   7  ozs.  3  drs.  fl. 

Dissolve  the  metabisulphite  and  bromide  in  part  of  the  distilled 
water  before  adding  the  pyrogallic  acid. 

A. 

Stock  solution ...       ...      1  oz. 

Distilled  water  to  make  altogether  ...       ...  20  ozs.  =  1  pt. 

B. 

Ammonia  ('890)        ...       ...       ...       ...       ...       2I  drs. 

Distilled  water  to  make  altogether  ...       ...  20  ozs.  =  1  pt. 

Mix  equal  parts  of  A  and  B  to  make  developer. 

Fixing  Solution. 

Hypo   1  lb. 

Water   I  qt. 

We  also  give  another  formula  for  pyro-ammonia  development 
without  the  metabisulphite  of  potass. 


Stock  Solution. 

Pyrogallic  acid  ...       ...       ...       ...  ...       I  oz.  av. 

Ammonium  bromide  ...        ...        ...        ...  ...        1   „  „ 

Sulphurous  or  sulphuric  acid  or  citric  acid  ...        1  drm. 

Distilled  water  to  make  altogether  ...        ...  7  ozs.  3  drs.  fl. 

Mix  the  acid  with  part  of  the  distilled  water  before  adding  the 
bromide  and  pyrogallic  acid. 

A. 

Stock  solution ...       ...       ...       ...       ...       ...       I  oz. 

Distilled  water  to  make  altogether  ...       ...  20  ozs.  =  I  pt. 

B. 

Liquid  ammonia  ('890)        ...       ...       ...       ...       2 A  drs. 

Distilled  water  to  make  altogether  ...       ...  20  ozs.  =  1  pt. 

Mix  equal  parts  of  A  and  B  to  make  developer. 

443 


APPENDIX. 

Fixing  Solution. 

Hypo   i  lb. 

Water  ...        ...        ...        ...        ...        ...        ...        I  qt. 

Clearing  Solution. 
Hydrochloric  acid      ...       ...       ...       ...       ...         ^  oz. 

Saturated  solution  of  alum   ...        ...        ...        ...      20  ozs. 

Pyro-Soda  Developer. 
Stock  Solution. 
Pyrogallic  acid  ...        ...        ...        ...        ...        1  oz.  av. 

Potassium  metabisulphite     ...       ...       ...       ...  40  grs. 

or  Sulphuric  acid       ...       ...       ...       ...       ...       1  dr.  fl. 

Distilled  water  to  make  altogether   10  ozs.  fl. 

A. 

Stock  solution ...       ...       ...       ...       ...       ...       3  ozs.  fl. 

Distilled  water  to  make  altogether  ...       ...       ...      20   „  fl. 

B. 

Sodium  carbonate  (crystals)    1 1  ozs.  av. 

or  „  „         (anhydrous)       ...       ...       ...  4  „  „ 

Sodium  sulphite  (recryst.)    ...       ...       ...       ...  15  „ 

Distilled  water  to  make  altogether  ...       ...       ...  80  „  „ 

Equal  parts  of  each  to  make  developer.  A  few  drops  of  a 
10  per  cent,  solution  of  potassium  bromide  may  be  added  to  the 
developer  when  necessary.  In  very  hot  weather  the  hypo  bath 
should  not  be  stronger  than  1  lb.  of  sodium  hyposulphite  to 
2  quarts  of  water. 

Photo- Mechanical  Plate. 

Development. 


A. 

Pyrogallic  acid    60  grs. 

Potassium  metabisulphite     ...        ...        ...        ...  60  „ 

Ammonium  bromide  ...       ...       ...       ...       ...  60  ,, 

Distilled  water  to  make       ...    ...  20  ozs. 

B. 

Ammonia  ('890)    2.\  drs. 

Distilled  water  to  make       ...       ...       ...       ...  20  ozs. 


Equal  parts  of  each  A  and  B  to  make  developer. 

444 


I.     PLATE-MAKERS'  FORMULA. 

Lantern- Plates. — Developers. 

Pyro-Ammonia. 
A. 

Pyrogallic  acid                               ...       ...       ...  40  grs. 

Ammonium  bromide  ...        ...        ...        ...        ...  40  „ 

Potass,  metabisulphite         ...        ...        ...        ...  120  ,, 

Distilled  water  to  make  altogether  ...       ...       ...  20  ozs.  fl. 

B. 

Liquid  ammonia        ...        ...        ...        ...        ...  150  mins. 

Distilled  water  to  make  altogether  ...       ...       ...  20  ozs.  fl. 

Equal  parts  of  A  and  B  to  make  developer.    This  formula  gives 

rich  warm  tones  with  suitable  exposure.  For  warm  black  tones 
the  following  may  be  used  : — 

A. 

Pyrogallic  acid           ...        ...        ...        ...        ...  30  grs. 

Sodium  sulphite        ...       ...       ...       ...       ...  100 

Sulphurous  acid  (or  citric  acid  5  grs.)       ...        ...  5  mins. 

Ammonium  bromide                       ...  ...        ...  30  grs. 

Distilled  water  to  make  altogether  ...  ..        ...  20  ozs. 

B. 

Liquid  ammonia  ("890)    ...        ...  40  mins. 

Distilled  water  to  make  altogether  ...       ...       ...  20  ozs.  fl. 

Equal  parts  of  A  and  B  to  make  developer.    A  rich  warm  black 

can  be  obtained  with  hydroquinone,  and  we  strongly  recommend 
the  following  formula  : — 

A. 

Hydroquinone...       ...       ...       ...  ...       ...  70  grs. 

Potass  metabisulphite    ...        ...  10  „ 

or  Sulphurous  acid    ...        ...        ...  ...        ...  15  mins. 

Potassium  bromide    ...        ...        ...  ...        ...  35  grs. 

Distilled  water  to  make  altogether  ...    20  ozs.  fl. 

B. 

Potassium  hydrate  (sticks)   140  grs. 

Sodium  sulphite      700  „ 

Distilled  water  to  make  altogether  ...  ...       ...  20  ozs. 

445 


APPENDIX. 


Equal  parts  A.  and  B.  to  make  developer.  Cold  but  brilliant 
black  tones  are  obtained  with  ferrous  oxalate,  adding  a  sufficient 
quantity  of  a  10  per  cent,  solution  of  potassium  bromide  to 
prevent  too  rapid  development. 

A. 

Ferrous  sulphate   

Sulphuric  acid  ...   

Distilled  water  to  make  altogether  .. 

B. 

Neutral  potass,  oxalate    ...      10  ozs.  av. 

Distilled  water  to  make  altogether   40  ,,  fl. 

Dissolve  the  potass,  oxalate  in  about  £  of  the  distilled  water, 
made  warm,  and  make  up  to  bulk  after  the  salt  is  dissolved.  The 
ferrous  sulphate  should  be  powdered  just  before  solution  in 
about  I  of  the  distilled  water,  to  which  the  sulphuric  acid  has 
been  previously  added.  Make  up  to  bulk  after  solution.  To 
make  developer,  add  1  part  of  A  to  4  of  B.  For  over  exposure, 
add  a  few  drops  to  the  mixed  developer  of  a  10  per  cent,  solution 
of  potassium  bromide. 

Fixing  Solution. 

Hypo   1  lb. 

Water   I  qt. 

Tone  or  colour  considerably  depends  on  exposure,  short  ex- 
posures favouring  colder  tones ;  also,  the  more  the  developer  is 
restrained  with  soluble  bromides,  the  warmer  the  tones  will  be, 
and  vice  versa. 

Edwards,  Austin,  "  Queen  "  Negative  Films.  Instructions. 
The  only  variation  in  working  which  need  be  made  when  using 
"Queen"  Films  instead  of  plates  are  simple  mechanical  ones, 
which  readily  suggest  themselves  in  handling  a  flexible  film  in 
lieu  of  a  rigid  glass  plate.  The  chemical  treatment  is  exactly 
the  same  as  for  plates,  any  developer  which  is  suitable  for  the 
one  is  equally  adapted  for  the  other ;  the  length  of  time  required 
for  development,  and  the  appearance  of  the  image  during  and 
after  development,  being  the  same  in  both. 

446 


5  ozs.  av. 
10  mins. 
20  ozs.  av. 


I.   plate-makers'  formulae. 


To  expose  "  Queen  "  Films  in  an  ordinary  dark  slide.  Put  the 
film  in  as  you  would  a  glass  plate,  and  then  place  a  piece  of  black 
cardboard  (12-sheet  thickness),  of  the  same  size  as  the  film,  at 
the  back ;  or  a  film  carrier  may  be  used.  The  slide  being  filled, 
draw  the  shutter,  and  carefully  dust  the  face  of  the  film  with  a 
camel-hair  brush  or  soft  piece  of  wash-leather  kept  for  this 
purpose.  Care  should  also  be  taken  to  have  the  slides  and  camera 
free  from  dust.  Spots  on  negatives  often  result  from  inattention 
to  these  precautions. 

Development.    Any  good  developer  may  be  used,  but  the 
following  Pyro  and  Soda  formula  is  specially  recommended.  It 
undoubtedly  gives  the  finest  possible  results  with  the  "Queen 
Films  of  either  speed  . 


The  "  Queen  "  Pyro  and  Soda  Developer. 
No.  1. 

Pyrogallic  acid     ...        ...         ..      I  oz.      or  30  grms. 

Nitric  acid  ...        ...        ...        ...  20  drops  ,,    I  c.cm. 

Water        ...        ...        ...        ...  80  ozs.     „    2  lits.  300  c.cm. 


Note. — No.  1  may  be  mixed  as  a  stock  solution,  if  preferred, 
by  using  only  8  ozs.  of  water  instead  of  80  ozs.,  and  diluting  to 
above  proportions  as  required. 


No.  2. 

Sulphite  of  soda   ...        ...        ...  10  ozs.  or  300  grms. 

Carbonate  of  soda  (crystals)      ...  9   „     „  250 

Water    80   „     „      2  lits.  300  c.cm. 


No.  3. 

Bromide  of  potassium     ...        ...      4  drms.  or    16  grms. 

Water       ...       ...    4  ozs.         114  c.cm. 

For  use,  mix  equal  parts  of  No.  1  and  No.  2.  Tor  landscape 
work  use  the  same,  with  two  minims  or  drops  of  No.  3  added  to 
each  ounce  of  the  mixed  developer.  In  case  of  under-exposure, 
or  for  subjects  possessing  great  contrasts  of  light  and  shade, 
dilute  the  developer  and  use  no  No.  3.     For  over-exposure 

447 


APPENDIX. 


restrain  by  adding  more  No.  3,  or  use  less  No.  2.  After  develop- 
ment, rinse  and  immerse  in  the  following 

Fixing  Bath. 
Hyposulphite  of  soda     ...       ...      I  lb.   or    500  grms. 

Water   40  ozs.  „  1,250  c.cm. 

This  is  most  conveniently  used  in  a  deep  porcelain  dish.  The 
precaution  should  be  taken  when  films  are  put  into  the  fixing 
bath  of  pressing  them  well  under,  so  that  they  are  perfectly 
covered  by  the  solution,  otherwise  stains  may  be  caused.*  The 
negatives  should  remain  in  the  fixing  bath  for  a  few  minutes 
after  they  are  apparently  fixed,  to  ensure  perfect  fixation.* 

Washing.  The  negatives  should  then  be  well  rinsed  and 
placed  in  a  grooved  washing  tank,  in  which  they  are  to  be  washed 
for  not  less  than  two  hours,  the  water  running  frequently  through 
the  tank,  or  being  frequently  changed. 

Drying.  When  sufficiently  washed,  hang  the  film  negative  up 
to  dry.  Spring  clips  are  most  convenient  for  this  purpose,  the 
films  being  suspended  by  one  corner. 

Edwards,  B.  J.  &  Co.'s  Isochromatic  and  Ordinary  Plates 
and  Films.  The  Dark  Room.  When  using  Isochromatic  films 
or  plates  great  care  must  be  taken  to  work  with  a  deep  ruby 
light  only.  Three  thicknesses  of  good  ruby  glass  or  two  of  ruby 
fabric  give  a  fairly  safe  working  window  for  ordinary  daylight. 
For  lamplight  the  protection  required  is  of  course  dependent  on 
the  strength  of  the  light  employed :  two  thicknesses  of  ruby 
glass  or  one  of  ruby  fabric  will  generally  be  found  sufficient,  but 
it  must  not  be  supposed  that  the  light  in  either  case  is  sufficiently 
non-actinic  to  have  no  action.  Care  should  be  taken  not  to 
expose  the  film  or  plate  more  than  is  necessary  even  to  this  light, 
especially  before  and  during  the  first  part  of  the  development. 
It  is  a  good  plan  to  cover  over  the  developing  dish  or  otherwise 
shield  it  from  the  light. 

Development  with  Pyrogallic.  Any  of  the  following  developers 
are  suitable  for  these  plates  or  films : — 

*  Special  attention  is  called  to  these  points  because  it  has  been  found  that 
nearly  all  troubles  in  working  films  are  due  to  disregard  of  one  or  other  of 
them. 

448 


I.     PLATE-MAKERS'  FORMULAE. 


Pyro  and  Ammonia  Developer. 


No.  i. 


Pyrogallic  acid 
Citric  acid  ... 
Water 


I    oz.  or     30  grms. 
40   grs.  or     3  „ 
*}\  ozs.  or  214  c.cm. 


No.  2. 


Strong  ammonia  (-88o) 
Bromide  of  potassium 


I  oz.  or  28  c.cm. 
120  grs.  or     8  grms. 


Distilled  water    7  ozs.  or  200  c.cm. 

The  above  will  keep  good  for  months  if  well  corked.  For  use 
dilute  1  part  No.  1  with  19  parts  of  water,  and  in  another  bottle 
1  part  No.  2  with  19  parts  of  water.  The  dilute  solutions  should 
be  made  fresh  every  day.  To  develope  a  correctly  exposed  plate 
or  film,  mix  equal  parts  of  these  two  solutions.  In  hot  weather, 
when  making  up  the  dilute  solutions  for  use,  add  4  parts  of 
No.  1  to  3  parts  of  No.  2,  instead  of  equal  parts  of  Nos.  1  and  2. 
In  no  case  should  the  quantity  of  No.  2  exceed  that  of  No.  1. 

Pyro  and  Soda  Developer  with  Metabisulphite. 
No.  1. 

Pyrogallic  acid     ...       ...       ...       1  oz.  or  30  grms. 

Metabisulphite  of  soda  (Boake's)        1  ,,  or  30  ,, 

Water    80  ozs.  or  2  litres  300  c.cm. 

Dissolve  the  metabisulphite,  and  then  add  the  pyro. 

No.  2. 

Carbonate  of  soda  (washing  soda)      12  ozs.  or  360  grms. 
Water    ...        ...      80        or  2  litres  300  c.cm. 


To  develop  mix  equal  parts  of  Nos.  1  and  2.  When  working  in 
the  summer  time  in  a  good  light,  with  full  exposure,  add  5 
minims  of  No.  3  to  each  ounce  of  developer  (or,  to  save  the 
trouble  of  measuring  small  quantities,  \\  ozs.  of  No.  3  may  be 


No.  3. 


Bromide  of  potassium 
Water   


I  oz.  or  30  grms. 
9  ozs.  or  250  c.cm. 


449 


APPENDIX. 


added  to  the  80  ozs.  of  No.  2) ;  in  winter  the  bromide  may 
generally  be  omitted,  and  also  for  rapid  shutter  exposures,  and 
portrait  work  in  the  studio.  This  developer  gives  exceedingly 
fine  and  delicate  negatives,  with  full  detail  in  the  high  lights,  and 
of  good  colour  for  printing. 


Pyro  and  Soda  Developer. 
No.  1. 

Pyrogallic  acid      ...       ...       ...  1  oz.  or  30  grms. 

Nitric  acid  ...       ...       ...       ...  20  drops  or  I  c.cm. 

Water       ...       ...       ...       ...  80  ozs.  or  2  litres  300  c.cm. 

No.  2. 

Sulphite  of  soda   10  ozs.  or  300  grms. 

Carbonate  of  soda  (crystals) — wash- 
ing soda    8  ,,    or  226  „ 

Water    80  „    or  2  litres  300  c.cm." 


No.  3. 

Bromide  of  potassium     ...       ...       1  oz.  or    30  grms. 

Water       ...       ...       ...        ...       9  ozs.  or  250  c.cm. 

To  develope  mix  equal  parts  of  Nos.  1  and  2,  and  add  10  minims 
of  No.  3  to  each  ounce  of  the  mixed  developer,  or,  instead,  3  ozs. 
of  No.  3  may  be  added  to  the  80  ozs.  of  No.  2.  For  rapid  shutter 
exposures  omit  the  bromide.  This  developer  gives  bold  vigorous 
negatives  of  a  neutral  grey  colour.  In  either  of  the  foregoing 
developers,  the  No.  1  solution  may  be  mixed  as  a  stock  solution, 
if  preferred,  by  using  only  8  ozs.  of  water  instead  of  80,  and 
diluting  to  above  proportions,  as  required. 

General  Notes.  Dust  the  face  of  the  plate  just  before  placing 
it  in  the  dish  for  development,  and,  putting  it  face  upwards,  pour 
the  mixed  developer  steadily  over  the  dry  plate,  removing  any 
air  bubbles  by  passing  a  flat  camel-hair  brush  (kept  specially  for 
this  purpose)  over  it  immediately  ;  rock  the  dish  gently,  taking 
care  to  keep  the  film  or  plate  well  covered  with  the  solution. 
When  using  pyro  developer,  where  a  plate  is  found  to  be  under- 
exposed, the  normal  developer  should  be  at  once  diluted  by  the 
addition  of  water  ;  in  some  cases  as  much  as  three  or  four  times 

45°  - 


I.   Plate-makers'  formula. 


its  bulk  of  water  may  be  added  with  advantage,  the  development 
proceeding  proportionately  slowly.  By  this  means  detail  is 
brought  out  in  the  shadows  without  permitting  the  high  lights 
to  gain  too  much  density.  Under-exposure  should  always  be 
avoided,  as  with  these  plates  or  films  a  considerable  amount  of 
over-exposure  can  be  controlled  in  development,  but  if  the  light 
has  not  acted  sufficiently  on  the  plate  no  process  of  development 
can  possibly  make  a  good  negative  of  it.  For  interiors  and  other 
subjects  possessing  great  contrasts  of  light  and  shade,  a  weak 
developer  should  always  be  used.  The  best  and  most  efficient 
method  of  correcting  over-exposure  is  that  introduced  by  Mr. 
Edwards  in  1888.  This  consists  in  using  a  separate  strong  but 
well-restrained  developer  as  a  redeveloper,  which  is  substituted 
for  the  normal  developer,  as  soon  as  over-exposure  is  recognised. 
When  developing  this  redeveloper  is  kept  ready  mixed  in  a 
measure,  and  if  the  detail  of  the  negative  rushes  up  too  quickly, 
indicating  over-exposure,  the  normal  developer  is  poured  off  and 
the  redeveloper  instantly  substituted  for  it  without  waiting  to 
wash  the  plate,  by  this  means  very  considerable  over-exposure 
can  be  satisfactorily  remedied,  the  redeveloper  giving  density 
without  bringing  out  much  more  detail.  This  method  of  tentative 
development  will  be  found  exceedingly  useful  when  developing 
a  number  of  various  or  unknown  exposures.  The  following  is 
the  formula  for  pyro.  and  ammonia  redeveloper ;  separate  formulae 
are  given  for  redevelopers  to  be  used  with  pyro  and  soda,  and 
hydrokinone  or  eikonogen : — 


Pyro  and  Ammonia  Redeveloper. 


No.  1. 


Pyro 

Citric  acid  ... 
Distilled  water 


1  oz.  or      30  grms. 

2  drs.  or      8  ,, 
32  ozs.  or  1000  c.cm. 


No.  2. 


Ammonia  ("88o)  ... 
Bromide  of  ammonia 
Distilled  water 


2  ozs.  or  60  c.cm. 
24  drs.  or  96  grms. 
32  ozs.  or  1000  cc.m. 


For  use  mix  equal  parts  of  Nos.  1  and  2 

451 


APPENDIX. 


Pyro  and  Soda  Redeveloper. 
No.  i. 

Pyro   

Metabisulphite  of  soda  (Boake's) 
Distilled  water   

No.  2. 

Carbonate  of  soda  (crystals)     ...       9  ozs.  or  250  grms. 
Bromide  of  potassium     ...       ...       2   „   or  60  „ 

Distilled  water    28  „   or  800  c.cm. 

For  use  mix  equal  parts  of  Nos.  1  and  2. 

Development  with  Hydrokinone  and  Eikonogen. 
Hydrokinone  Developer. 

No.  1. 

Hydrokinone   

Sulphite  of  soda  ...   

Bromide  of  potassium   

Distilled  boiling  water  to  make  ... 

No.  2. 

Carbonate  of  potash    \  oz.  or     15  grms. 

Distilled  water  to  make   12   ozs.  or  340  c.cm. 

First  dissolve  the  hydrokinone,  and  then  add  the  sulphite  and 
bromide.  For  use  mix  equal  parts  of  Nos.  1  and  2.  In  cases  of 
slight  over-exposure  add  a  few  drops  or  minims  of  a  10  per  cent, 
solution  of  bromide  of  potassium  to  each  ounce  of  developer 
more  or  less  according  to  extent  of  over-exposure.  For  con- 
siderable over-exposure  use  the  redeveloper.  For  under-exposure 
pour  off  the  hydrokinone  developer  and  finish  development  with 
the  eikonogen  developer  given  below. 

Eikonogen  Developer. 

Eikonogen   \  oz.  or     14  grms. 

Carbonate  of  potash       ...       ...  1        or     30  „ 

Sulphite  of  soda   ...       ...       ...  2   ozs.  or  60  grms. 

Distilled  boiling  water    20     „   or  600  c.cm. 

FiTSt  dissolve  the  eikonogen,  then  the  sulphite,  and  lastly  the 

45  2 


I  oz.  or     30  grms. 
1  „   or     30  „ 
28  ozs.  or  800  c.cm. 


\  oz.  or      7  grms. 
1    „  or     30  „ 
7  grs.  or      £  grm. 
12   ozs.  or  340  c.cm. 


I.    plate-makers'  formula. 


carbonate  of  potash.  This  will  be  found  a  very  useful  developer 
for  snapshot  work  and  portraiture  ;  for  ordinary  landscape  work 
a  mixture  of  this  and  the  above-given  hydrokinone  developer  is 
to  be  preferred  to  eikonogen  alone.  One  part  of  the  eikonogen 
to  two  parts  of  the  mixed  hydrokinone  developer  will  be  found  to 
work  well,  but  the  proportions  may  be  varied  to  produce  a 
developer  possessing  the  required  characteristics,  eikonogen 
tending  to  softness  and  fulness  of  detail,  and  hydrokinone  to 
bright  shadows  and  full  density.  Instead  of  mixing  the  developers, 
the  development  may  be  commenced  with  eikonogen,  and  when 
the  detail  is  sufficiently  out,  hydrokinone  substituted  for  it,  without 
waiting  to  wash  the  negative,  and  the  development  finished  with 
this,  or  in  case  of  much  over-exposure  with  the  following  hydro- 
kinone redeveloper : — 

Redeveloper  For  Hydrokinone  or  Eikonogen. 
No.  i. 

Hydrokinone   

Sulphite  of  soda  

Bromide  of  potassium   

Distilled  boiling  water  to  make  ... 

No.  2. 

Carbonate  of  soda  (crystals)      ...  2  ozs.  or   60  grms. 

Sulphite  of  soda   2  ,,   or   60  ,, 

Distilled  water  to  make   12   „   or  340  c.cm. 

For  use  mix  equal  parts  of  Nos.  1  and  2. 

Fixing. 

After  development  well  wash  the  negative  under  the  tap,  and 
immerse  in  the  following  : — 

Fixing  Bath. 

Hyposulphite  of  soda    6  ozs.  or  180  grms. 

Water    I  pt.  or  600  c.cm. 

This  is  most  conveniently  used  in  a  deep  porcelain  dish.  The 
precaution  should  be  taken  when  films  are  put  into  the  fixing 
bath,  of  keeping  them  well  under  so  that  they  are  perfectly 
covered  by  the  solution,  otherwise  stains  may  be  caused.  The 

453 


£  oz.  or  7  grms. 
2   ozs.  or  60 

i  oz.  or       7  „ 
12   ozs.  or  340  c.cm. 


APPENDIX. 


negatives  should  remain  in  the  fixing  bath  for  2  or  3  minutes 
after  they  are  apparently  fixed,  so  as  to  ensure  perfect  fixation. 
If  an  acid  fixing  bath  is  preferred,  add  1  oz.  of  metabisulphite  of 
soda  (Boake's)  to  the  6  ozs.  of  hyposulphite  of  soda,  the  addition 
of  the  metabisulphite  tends  to  keep  the  fixing  bath  clear,  and 
prevents  discoloration  of  the  negative. 

Clearing. 

When  fixed  the  negatives  should  be  well  rinsed  under  the  tap, 
and  if  they  have  been  developed  with  pyro,  put  into  a  dish 
containing  the  following  clearing  solution  for  about  a  minute.  If 
developed  with  a  developer  other  than  pyro,  the  clearing  bath  is 
not  necessary,  and  the  negatives  may  be  removed  direct  from  the 
hypo  to  the  washing  tank. 

Clearing  Solution. 

Alum    1    oz.  or   30  grms. 

Citric  acid   I     „     „  30 

or  Sulphuric  acid   \  ,,     „      7  „ 

Sulphate  of  iron    ...       ...       ...  3   ozs.  „    90  „ 

Water    20     „    fl  600  c.cm. 

Washing. 

After  treating  with  the  clearing  solution,  the  negatives  should 
be  again  well  rinsed,  and  placed  in  a  grooved  washing  tank,  in 
which  they  are  to  be  washed  for  not  less  than  2  hours,  the  water 
running  continuously  through  the  tank  or  being  frequently 
changed.  In  placing  film  negatives  in  the  grooves  it  is  best  to 
put  two  films  back  to  back  in  one  groove,  as  they  stand  up  better 
in  this  way.  When  finished  washing,  hang  the  film  negatives  up 
to  dry  ;  spring  clips  are  most  convenient  for  this  purpose,  the 
films  being  suspended  by  one  corner. 

Varnishing. 

The  negatives  may  be  printed  from  as  soon  as  perfectly  dry, 
but  if  this  be  done  without  previously  protecting  them  with  a 
coat  of  varnish,  there  is  always  a  danger  of  the  silver  from  the 
sensitised  paper  staining  the  negatives. 

Special  Transparency  Plates  for  Lantern  Slides. — Instructions 
for   Use.     They   are   equally   suitable   for   contact  printing 

454 


I.   plate-makers'  formulae. 


or  reductions  in  the  camera.  For  contact  printing  by  gas- 
light, using  the  light  of  a  good  fish-tail  burner  at  a  distance 
of  12  inches  from  the  flame,  any  time  from  10  to  60  seconds 
exposure  may  be  required,  according  to  the  density  of  the 
negative,  more  exposure  being  necessary  when  it  is  intended 
to  develope  with  pyro  for  brown  tones,  than  for  black  tones 
with  hydrokinone  or  amidol.  Very  thin  negatives  should  be 
exposed  at  a  greater  distance  from  the  light  and  very  dense 
ones  nearer  to  it.  Exposure  may  also  be  made  by  diffused 
daylight  in  the  dull  light  of  an  ordinary  room  ;  it  is,  however, 
far  more  difficult  to  judge  the  correct  time  of  exposure,  therefore 
it  is  preferable  to  use  artificial  light.  It  is  important  that  as 
nearly  as  possible  correct  exposure  be  given  ;  under-exposed 
plates  when  developed  appear  hard  with  black  shadows,  and 
want  of  detail  in  the  half  tones,  while  very  much  over-exposed 
pictures  are  usually  thin  and  flat,  without  sufficient  contrast. 
The  colour  obtained  is  also  dependent  on  the  length  of  exposure. 
The  best  indications  of  the  correct  timing,  or  otherwise,  of  the 
exposure  are  the  time  taken  before  the  image  begins  to  appear, 
and  the  time  necessary  to  attain  the  required  density.  For 
lantern  slides,  at  least  some  portion  of  the  highest  lights  in  the 
picture  should  be  represented  by  absolutely  clear  glass,  without 
a  trace  of  fog  or  deposit  of  any  kind,  which  would  detract  from 
the  brilliancy  of  the  image.  These  plates  cannot  be  satisfactorily 
developed  with  any  of  the  usual  formulae  for  negative  work,  but 
either  of  the  following  formulae  will  give  results  perfect  in  every 
way.  To  develop,  place  the  exposed  plate  in  the  developing 
tray,  and  pour  over  the  developer  without  previously  wetting 
the  film :  all  danger  of  air  bubbles  may  be  avoided  by  passing 
a  brush  over  the  surface  of  the  plate  immediately  after  pouring 
on  the  developer. 

Pyro  and  Ammonia  Developer  for  Warm  Tones 
No.  1. 

Pyrogallic  acid    ...        I    oz.    or   30  grins. 

Sulphite  of  soda   4  ozs.  ,,   120  ,, 

Citric  acid   ...         |  oz.    „       8  „ 

Water    16   ozs.       460  c.cm. 

First  dissolve  the  sulphite  and  citric  acid,  and  then  add  the 
pyrogallic. 

455 


APPENDIX. 


No.  2. 

Bromide  of  ammonium    I    oz.    or    30  grins. 

Liq.  ammonia  (880)        ...        ...       5^  drs.   „    20  c.cm. 

Water  to  make     ...       ,..       ...  16   ozs.   ,,460  „ 

For  use  mix  one  part  of  No.  1  and  three  parts  of  No.  2, 
and  dilute  with  water  to  double  the  quantity.  The  mixed 
developer  may  be  used  over  again  for  several  plates.  For 
lantern  slides  and  transparencies  from  very  thin  negatives  dilute 
the  stock  solution  with  less  water.  For  contact  printing  under 
the  conditions  given  above,  the  exposure  for  negatives  of  medium 
printing  densities  will  be  from  20  to  60  seconds.  If  the  correct 
time  has  been  given  the  image  should  begin  to  appear  in  from 
40  to  50  seconds,  and  the  development  be  complete  in  about 
five  minutes. 

Hydrokinone  Developer  for  Black  Tones. 

Hydrokinone       ...       ...  ...  60  grs.  or     3  grms. 

Sulphite  of  soda   ...  2  ozs.         45  ,, 

Carbonate  of  soda  (crystals)  ....  4  „  ,,    90  ,, 

Carbonate  of  potash       ...  ...  2  ,,  „    45  „ 

Bromide  of  potassium     ...  ...  40  grs.  „      2  „ 

Hot  distilled  water        ...  ...  20  ozs.  „  450  c.cm. 

For  black  and  white  line  subjects  add  1  drachm  of  a  60-grain 
solution  of  bromide  of  potassium  to  each  ounce  of  developer. 
Dissolve  the  hydrokinone  in  the  water,  and  add  the  other 
ingredients  in  the  order  named.  This  developer  will  keep  good 
for  at  least  a  month  ;  it  can  be  used  over  again  for  several  plates. 
Exposure  for  contact  printing  as  above,  10  to  30  seconds.  The 
image  should  begin  to  appear  in  about  40  seconds  to  a  minute, 
and  the  development  be  completed  in  about  4  minutes. 

Amidol  Developer  for  Black  Tones. 
Amidol      ...       ...       ...       ...     80  grs.   or     5  grms. 

Soda  sulphite    ...       2   ozs.    „    45  „ 

Bromide  of  potassium     ...       ...         £  oz.     „    15  „ 

Water    12  ozs.    „  360  c.cm. 

This  developer  is  to  be  used  without  dilution,  except  when 
working  from  a  very  strong  negative,  when  it  can  be  diluted 
with  an  equal  amount  of  water.  It  may  be  used  repeatedly 
without  apparent  loss   of  developing  power.    With  correct 

456 


I.     PLATE-MAKERS'  FORMULAE. 


exposure  it  yields  slides  of  a  very  fine  black  colour.  Exposure 
for  contact  printing  the  same  as  for  hydrokinone.  Time  of 
development  about  8  minutes.  These  plates  may  be  developed 
in  either  yellow  or  ruby  light,  the  plate  should  be  examined  by 
looking  through  it  from  time  to  time,  taking  care  not  to 
expose  it  too  much  to  the  light.  With  pyro  developer  the 
transparency  appears  of  nearly  the  same  density  before  fixing 
as  when  finished,  but  when  using  hydrokinone  or  amidol  the 
image  must  be  developed  to  look  much  denser,  as  there  is 
considerable  reduction  in  the  fixing  bath.  As  soon  as  the 
transparency  is  sufficiently  dense  in  the  shadows,  place  it  direct 
in  the  fixing  bath,  without  previous  washing. 

Fixing  Bath. 

Hyposulphite  of  soda     ...       ...       4  ozs.   or  120  grms. 

Water    20    ,,      „  600  c.cm. 

Leave  in  this  for  at  least  5  minntes,  and  then  wash  thoroughly 
for  an  hour  or  more.  To  secure  greater  brilliancy  and  dissolve 
away  any  deposit  caused  by  impurities  in  the  washing  waters, 
the  transparency  should  be  immersed  for  2  or  3  minutes  in  some 
of  the  following  clearing  solution  contained  in  a  dish,  using  fresh 
for  each  plate.  The  transparency  is  afterwards  to  be  well 
washed  for  ten  minutes  : — 

Alum         ...       ...       ...       ...       1  oz.   or     30  grms. 

Citric  acid   1  ,,     „      30  „ 

Water    20  ozs.  „    600  c.cm. 

If,  from  an  error  in  the  exposure  or  want  of  quality  in  the 
original  negative,  the  lantern  slide  or  transparency  is  still 
wanting  in  sparkle,  through  the  high  lights  being  veiled,  it  may 
be  effectually  cleared  either  at  this  stage  or  after  being  dried, 
by  using  Mr.  Howard  Farmer's  reducer,  made  as  follows  : — 

No.  1. 

Ferridcyanide  of  potassium  ...  60  grs.  or  4  grms. 
Water    20  ozs.    „  600  c.cm. 

No.  2. 

Hyposulphite  of  soda    I  oz.    or   30  grms. 

Water    20  ozs.    „  600  c.cm. 

For  use  Mix  No.  1  and  No.  2  in  equal  proportions.  Place  the 
transparency  in  a  dish  and  flood  it  with  the  solution  ;  the  dish 

457 


APPENDIX. 


must  be  continually  rocked  and  the  transparency  carefully 
watched,  and  removed  instantly  the  highest  lights  are  cleared, 
which  will  not  usually  take  more  than  I  or  2  minutes :  it  is  then 
to  be  again  well  washed  before  being  dried.  This  reducer  is  in 
practice  very  useful,  but  requires  using  with  great  care,  as  it  is 
capable  of  dissolving  away  the  whole  of  the  image,  should  the 
transparency  be  left  in  too  long.  When  thoroughly  washed,  the 
lantern  slides  or  transparencies  should  be  allowed  to  dry 
spontaneously,  and  are  then  ready  for  binding  or  mounting  in 
the  usual  way.  If  desired,  they  may  be  previously  varnished, 
using  either  our  crystal  varnish  or  protective  varnish  for  films. 

Gelatino-Chloride  Plates. — Instructions  for  bse.  Exposure. 
These  plates  are  chiefly  intended  for  contact  printing  under 
a  negative  in  an  ordinary  pressure  frame  ;  when  used  in  this 
way  they  are  extremely  sensitive  to  daylight,  the  time  of 
exposure  varying  from  1  second  to  15  or  20  seconds,  accord- 
ing to  the  power  of  the  light  and  the  density  of  the  negative. 
Full  exposure  in  a  dull  light  usually  gives  the  best  results. 
With  thin  or  weak  negatives  it  is  better  to  cover  the  printing 
frame  during  exposure  with  a  sheet  of  opal  glass  or  white 
tissue  paper,  giving  sufficient  exposure  to  compensate  for 
the  loss  of  light.  A  convenient  method  of  printing  by  artificial 
light  consists  in  burning  an  inch  or  two  of  magnesium  ribbon 
at  a  distance  of  12  inches  from  the  printing  frame.  These  plates 
can  also  be  used  for  making  enlarged  or  reduced  positives  from 
negatives  in  the  camera,  but  for  this  purpose  a  much  longer 
exposure,  probably  5  to  10  minutes,  in  a  good  light  will  be  found 
*  necessary  to  ensure  success. 

Development.    Make  two  stock  solutions  as  follows  : — 
No.  1. 

Neutral  oxalate  of  potash      2  ozs. 

Chloride  of  ammonium        ...       ...       ...       ...     40  grs. 

Distilled  water  ...       ...    ...      20  ozs. 

No.  2. 

Sulphate  of  iron        ...       ...       ...       ...       ...       4  drms. 

Citric  acid    2  „ 

Alum     2  „ 

Distilled  water  ...       ...       ...       ...       ...  20  ozs. 


458 


I.     PLATE-MAKERS  FORMULA. 


The  above  solutions  will  keep  indefinitely.  When  required  for 
use  mix  equal  portions  of  the  above  solutions,  adding  No.  2  to 
to  No.  i  to  form  the  developer,  place  the  exposed  plate  film 
uppermost  in  a  porcelain  dish,  and  pour  over  rapidly  and  evenly 
the  mixed  developer,  rock  the  dish  during  the  progress  of 
development  (which  may  be  examined  from  time  to  time  by 
yellow  or  non-actinic  light),  when  sufficient  density  is  obtained, 
which  will  usually  be  in  about  2  minutes,  pour  off  the  developer 
into  a  measure,  and  flood  the  plate  with  water  and  wash  well 
under  the  tap.  The  above  developer  with  moderate  exposure 
will  give  positives  of  a  warm  black  colour,  still  warmer  tone  may 
be  easily  obtained  by  simply  diluting  the  mixed  solutions  with 
an  equal  quantity  of  distilled  water,  or  by  adding  to  each  ounce 
2  or  3  drops  of  a  20-grain  solution  of  bromide  of  potassium,  and 
proportionally  increasing  the  time  of  exposure.  Short  exposure 
and  rapid  development  will  give  black  tones,  while  full  exposure 
and  slow  development  will  give  warm  brown  or  red  tones  to  the 
transparency.  It  will  be  found  a  good  plan  to  make  up  two 
separate  portions  of  developer,  strong  and  weak,  and  commence 
with  latter ;  should  the  plate  prove  to  be  under-exposed  the 
developer  must  be  poured  off,  and  the  more  concentrated  solution 
used  to  bring  out  the  picture  and  complete  development.  This 
method  will  allow  considerable  latitude  in  the  time  of  exposure. 
Several  plates  may  be  developed  in  the  same  solution,  but  the 
developer  gradually  loses  its  energy  and  will  not  keep  long  after 
being  mixed. 

Fixing. 

Hyposulphite  of  soda  ...       ...    2  oz-. 

Water   16  „ 

Pour  sufficient  of  the  above,  when  dissolved,  into  a  porcelain 
dish  and  immerse  the  developed  and  washed  plate  for  2  or  3 
minutes,  or  until  fixed,  then  rinse  thoroughly  under  the  tap  and 
apply  the  following  : — 

Sulphuric  acid    I  oz. 

Saturated  solution  of  alum   ...       ...       ...       ...      20  ozs. 

Pour  a  small  quantity  of  the  above  repeatedly  over  the  plate  for 
about  half  a  minute,  or  until  the  slight  deposit  of  oxalate  of  lime 
(caused  by  the  washing  water)  is  dissolved   away,  and  the 

459 


APPENDIX. 


picture  becomes  bright  and  clear.  The  high  lights  of  the 
transparency  should  be  perfectly  bare  glass  without  a  trace 
of  deposit  of  any  kind  ;  as  soon  as  cleared  wash  well  in  repeated 
changes  of  water,  and  allowed  to  dry  spontaneously. 

Caution.  Great  care  must  be  taken  that  not  the  faintest  trace 
of  hyposulphite  of  soda  comes  into  contact  with  the  developing 
solution  or  with  the  plate  before  or  during  development. 
Separate  dishes  must  be  used  for  each  solution.  The  dishes, 
as  well  as  the  hands  of  the  operator,  should  be  frequently 
washed  and  kept  scrupulously  clean  during  the  various  mani- 
pulations, otherwise  the  films  are  liable  to  become  stained  and 
discoloured.  When  quite  dry  the  transparencies  may  be 
varnished  with  good  clear  negative  varnish  applied  with  heat 
in  the  usual  way. 

Bromide  Opals. — Instructions  for  Use.  Exposure.  Place 
the  opal  plate  film-side  next  to  the  negative  in  an  ordinary 
printing  frame,  and  expose  to  the  light  of  a  paraffin  lamp, 
or  by  preference,  that  of  an  ordinary  fish-tail  gasburner,  at 
a  distance  of  2  feet  from  the  flame,  for  from  12  to  24  seconds, 
according  to  the  density  of  the  negative. 

Development.  The  following  formula  will  be  found  to  give 
very  satisfactory  results. 

Stock  Solutions. 
No.  1. 

Oxalate  of  potash    60  grms.  or  2  ozs. 

Chloride  of  ammonium    ...       ...       3     »»  »»  4^  &rs. 

Bromide  of  potassium     ...       ...       \\    ,,  „  20  „ 

Distilled  water    500  c.cm.  „  16  ozs. 

No.  2. 

Sulphate  of  iron   15  grms.  or  4  drms. 

Citric  acid           ...   8    „  „    2  „ 

Alum    8    „  ,,     2  „ 

Distilled  water    500  c.cm.  „  16  ozs. 

Having  mixed  equal  parts  of  the  above  solutions  (adding  always 
No.  2  to  No.  1),  place  the  exposed  opal  film  uppermost  in 
a  developing  dish  and  pour  the  mixture  evenly  over  the  plate, 
rock  the  dish  during  the  development,  and  watch  its  progress 

460 


I.     PLATE-MAKERS'  FORMULAE. 


by  a  ruby  or  deep  yellow  light.  When  the  image  appears  to 
have  acquired  the  detail  and  vigour  desired  in  the  finished 
picture,  wash  the  plate  well  under  a  tap  for  2  minutes  and  then 
immerse  for  10  minutes  in  the 

Fixing  Solution. 

Hyposulphite  of  soda    120  grms.   or  4  ozs 

Water   500  c.cm.    „  16  „ 

The  plate  must  now  be  well  washed  in  running  water  for  1  hour 
to  remove  the  hyposulphite  of  soda,  when  it  will  be  ready  for 
toning  in  the  sulpho-gold  toning  bath  to  a  rich  velvety  black. 

Stock  Solutions  for  Toning. 
No.  1. 

Chloride  of  gold    ...       1  grm.   or  15  grs. 

Distilled  water    ...    220  c.cm.    „    8  ozs. 

No.  2. 

Acetate  of  soda     ...    30  grms.  or    I  oz. 

Sulphocyanide  of  ammonium     ...  4    „  „     I  drm. 

Distilled  water  to  make  ...       ...  250  c.cm.  8  ozs. 

When  the  desired  shade  has  been  obtained,  the  picture  should 
be  well  rinsed  under  the  tap,  and  it  may  now  be  cleared  of  the 
slight  deposit  of  oxalate  of  lime  (caused  by  the  washing  water) 
by  pouring  over  or  immersing  it  for  half  a  minute  in  the 
following 

Clearing  Solution. 

Sulphuric  acid    15  grms.   or      \  oz. 

Saturated  solution  of  alum        ...    600  c.cm.         20  ozs. 

After  which  it  should  be  thoroughly  washed  to  complete  the 
process.  When  quite  dry  the  opal  can  be  finished  in  mono- 
chrome or  water  colours  as  may  be  desired,  or  may  be  varnished 
with  crystal  varnish. 

Caution.  It  is  of  the  greatest  importance  that  not  the 
slightest  trace  of  hyposulphate  of  soda  be  allowed  to  contaminate 
the  dishes  or  measures  employed  in  developing  or  toning  the 
opals.  Therefore  great  care  should  be  exercised  and  the  hands 
well  washed  between  the  various  operations. 

46 1 


APPENDIX. 


Elliott  &  Son's  "  Barnet,"  "  Studio,"  and  "  Rocket "  Plates. 

Pyro  and  Ammonia  (io  per  cent.  Solution). 

No.  i  Solution. 

Ammonia  (-88o)   I  oz. 

Water     9  ozs. 

No.  2  Solution. 

Bromide  of  ammonium  ...       ...       ...       ...       ...      I  oz. 

Water  to  make  10  ozs. 

No.  3  Solution. 

Pyro    1  oz. 

Water  to  make  ...       ...       ...       ...       ...       ...    to  ozs. 

Citric  acid  (pure)         ...       ...       ...       ...       ...    30  grs.  - 

For  studio  use :  Take  80  minims  No.  1 ;  40  minims  No.  2  ; 
20  minims  No.  3  ;  and  make  up  to  2  ozs.  with  water. 

For  outdoor  work  :  Take  80  minims  No.  1  ;  60  minims  No.  2  ; 
40  minims  No.  3  ;  and  make  up  to  2  ozs.  with  water. 

For  specially  quick  exposures  with  "Rocket"  plates:  120 
minims  No.  1  ;  20  minims  No.  2  ;  20  minims  No.  3  ;  and  make 
up  to  2  ozs.  with  water. 

Pyro  and  Soda  Developer. 

No.  1  Solution. 

Pyro    I  oz.  . 

Water   86  ozs. 

Nitric  acid  (pure)   20  drops. 

No.  2  Solution. 

Pure  sulphite  soda       ...       ...       ...    10  ozs. 

Pure  carbonate  soda  (crystals)  ...       ...       ...      9  „ 

Water    ...       ...       ...   86  „ 

Use  equal  parts  of  No.  1  and  No.  2,  and  dilute  with  equal  bulk 
of  water.  To  each  ounce  add  1  or  2  drops  of  a  10  per  cent, 
solution  of  bromide  of  potassium. 

462 


I.   plate-makers'  formul/e. 


Eikonogen  Developer. 

No.  i  Solution. 

Eikonogen   

Sulphite  of  soda   

Hot  water  ...   

No.  2  Solution. 

Common  washing  soda   

Water  

Use  equal  parts  of  No.  i  and  No.  2. 

Hydroquinone  Developer 
No.  i  Solution. 

Hydroquinone  

Sulphite  soda   

Citric  acid   

Bromide  potassium   

Distilled  water  ... 

No.  2  Solution. 

Caustic  soda   

Distilled  water  ... 
Use  equal  parts  of  No.  I  and  No.  2. 


4  ozs. 
6o  ., 


12  OZS. 

8o  ,. 


[6o  grs. 
2  ozs. 
6o  grs. 

20  ozs. 


[60  grs. 
20  ozs. 


Clearing  Solution. 

Chrome  alum     ...       ...       ...       ...  ...  ...  2  ozs. 

Citric  acid                                       ...  ...  ...  1  oz. 

Water                                             ...  ...  ...  20  ozs. 

"  Bamef  Lantern  Transparency  Plates.  For  cold  or  warm 
tones  (according  to  exposure  and  development). 

Instructio7is  for  Use. — Contact  Printing.  For  black  tones  the 
exposure  required  is  about  ten  seconds  at  the  distance  of  a  foot 
from  an  ordinary  gas  flame  ;  the  developer  to  be  used  is  either 
No.  1  or  No.  2.  To  secure  warm  tones  it  is  necessary  to  increase 
the  exposure  to  two  or  three  minutes  and  use  either  No.  3  or 
No.  4.  To  obtain  still  warmer  (reddish)  tones  increase  the  ex- 
posure still  further  to  five  or  six  minutes,  and  develop  with  No.  5. 

Reducti07is  in  the  Camera. — For  black  tones  with  stop  //16  in 
bright  diffused  light  from  a  £-plate  negative  an  exposure  of  about 
ten  seconds  is  required,  using  No.  1  or  No.  2  for  developing. 

463 


APPENDIX. 


For  warm  tones  increase  the  exposure  to  two  or  three  minutes, 
and  using  for  developer  either  No.  3  or  No.  4.  For  still  warmer 
tones  further  increase  the  exposure  to  five  or  six  minutes,  and 
develop  with  No.  5. 

Formula  for  Developers. 

Note. — In  cold  weather  all  solutions  should  be  raised  to  a 
temperature  of  6o°. 

No.  1.  Cold  Black  Tones. 
A. 

Metol    ...       ...   400  grs. 

Soda  sulphite  ...    ...       ...       ...       8  ozs. 

Water   80  „ 

B. 

Carbonate  of  potash  ...    ...1,200  grs. 

Ammonium  bromide  ...    ...       ...    240  „ 

Potassium  bromide   480  „ 

Water   80  ozs. 

Take  equal  parts  of  A  and  B. 

Note. — The  ammonium  bromide  is  necessary  for  the  production 
of  absolutely  cold  black  tones  ;  a  larger  quantity  is  not  re- 
commended as  it  tends  to  produce  a  slight  veil  in  the  high  lights. 
Length  of  time  in  developing  about  two  minutes. 

No.  2.  Warm  Black  Tones.  - 
A. 

Hydrokinone   640  grs. 

Soda  sulphite  ...       ...       ...       ...       ...       ...  8  ozs. 

Potassium  bromide    ...                 ...       ...       ...  120  grs. 

Water   80  ozs. 

B. 

Sodium  hydrate   640  grs. 

Water   80  ozs. 

Take  equal  parts  of  A  and  B.  This  produces  a  very  pleasing 
warm  black.    Length  of  time' in  developing  about  two  minutes. 

464 


I.    plate-makers'  formula 


No.  3.  Warm  Brown  Tones. 


A. 

Pyro      1  oz. 

Soda  sulphite   4  ozs- 

Water   80  „ 

B. 

Carbonate  of  ammonia         ...        ...        ...        ...  900  grs. 

Potassium  hydrate     ...        ...        ...        ...        ...  75°  » 

Ammonium  bromide  ...        ...        ...        ...        ...  600  „ 

Water                      ...       ...       ...    80  ozs. 


Take  equal  parts  of  A  and  B.  Length  of  time  in  developing 
about  two  minutes. 

No.  4.  Or  the  following  may  be  used  : — Take  equal  parts  of 
No.  2  formula  and  add  to  each  ounce  3  grs.  carbonate  of  ammonia 
and  3  grs.  of  ammonium  bromide.  Length  of  time  in  developing 
about  three  or  four  minutes. 

No.  5.  Very  Warm  (Reddish)  Tones.  Take  equal  parts  ot 
No.  2  formula  and  add  to  each  ounce  6  grs.  of  carbonate  of 
ammonia  and  6  grs.  ammonium  bromide.  Lengtji  of  time  in 
developing  about  eight  minutes. 

Fixing  Bath. 

We  recommend  the  bath  not  to  be  made  stronger  than — 

Hypo   5  02s. 

Water   ...    ...       ...      20  „ 

Clearing  solutions  will  not  be  found  necessary  with  these  plates. 

Hill-Norris  Dry  Collodion  Plate.— Instructions  for  use. 
Remarks.  These  plates  being  isochromatic,  should  only  be 
developed  in  a  ruby  light;  ordinary  canary  medium  alone  is 
unsuitable. 

Exposure  The  exposure  required  is  about  the  same  as  that 
of  the  best  gelatine  plates  on  the  market. 

Development :  These  plates  while  wet  being  soft  and  pappy, 
like  wet  collodion,  must  not  be  touched  or  brushed  during  de- 
velopment. They  may  be  put  straight  into  the  developer,  i.e., 
without  previous  wetting  ;  the  latter  does  not  recede  from  the 

465  H  H 


APPENDIX. 


surface  as  in  the  case  of  gelatine,  neither  do  any  air-bells  attach 
themselves  to  the  film.  Enough  developer  should  be  used  in 
a  suitable  dish  to  keep  the  plate  always  well  covered  with  the 
developing  solution.  All  the  customary  reducing  agents,  e.g., 
iron,  pyrogallol,  hydroquinone,  eikonogen,  can  be  used,  but 
ammonia  is  not  so  good  an  accelerating  agent  as  the  fixed 
alkalies ;  and  the  latter,  inasmuch  as  they  allow  less  exposure 
to  be  given,  are  therefore  to  be  preferred.  These  plates  can 
be  built  up  with  silver  and  pyro  after  fixing,  as  in  the  old  collodion 
process.  The  temperature  of  the  developing  room  and  solutions 
should  not  be  below  6o°  F.  As  a  guide  we  append  several 
formulae  for  developing. 

Hydroquinone — Potash. 
No.  i. 

Sodium  sulphite        ...       3,200  grs.,  or  7  ozs.,  137^  grs.  av. 
Potassium  bromide    ...       ...       ...       ...       ...     70  grs. 

Potassium  hydrate     ...       ...       ...       ...       ...    1  oz.  av. 

Water   26  ozs. 

«  No.  2. 

Hydroquinone                                                 ...  32  grs. 

Sodium  sulphite    160  „ 

Water    2  ozs. 

If  tentative  development  is  practised,  the  hydroquinone  solution 
should  be  withheld  in  part  for  a  time.  For  ^-plate,  take  3  drms. 
of  No.  1,  and  \  drm.  of  No.  2,  and  fill  up  with  water  to  2  ozs. 

Hydroquinone — Soda. 
No.  1. 

Hydroquinone           ...       ...       ...    1 60  grs. 

Sodium  sulphite        ...       ...       ...       ...       ...  2  ozs. 

Citric  acid       ...       ...       ...       ...       ...       ...  60  grs. 

.  •  <  Potassium  bromide    ...                            ...       ...  40  ,, 

Water   20  ozs. 

'    -  No.  2. 

Sodium  hydrate   ...    160  grs. 

Water  ...       ...       ...       ...   20  ozs. 

Mix  equal  parts  and  add  an  equal  quantity  of  water. 

466 


I.     PLATE-MAKERS'  FORMULAE. 

Pyro-Soda  (Carb.). 

Sodium  sulphite    25  grs. 

Sodium  carbonate  (not  bicarbonate)         ...       ...      25  ,, 

Water   ...       ...       ...       ...       ...       I  oz. 

One  to  3  grs.  of  dry  pyrogallol  to  be  added  to  each  ounce  of 
developer  used.  If  tentative  development  is  practised,  the  pyro 
should  be  withheld  in  part  in  preference  to  the  alkali. 

Ferrous  Oxalate. 
No.  1. 

Potassium  oxalate     ...       ...       ...       ...       ...      14  ozs. 

Water   50 

No.  2. 

Protosulphate  of  iron  ...        ...        ...        ...        ...      4.^  ozs. 

Acid  sulphuric  ...        ...        ...        ...        ...      2  drops. 

Water     ...    8  ozs. 

For  ^-plate  take  i£  oz.  of  No.  1  and  3  drms.  of  No.  2. 

Fixing  Solutions. 
No.  1. 

Potassium  cyanide     ...       ...       ...       ...       ...       1  oz. 

Water  ...       ...      ...      10  ozs. 

Rinse  well  under  tap. 

No.  2. 

Sodium  hyposulphite   4  ozs. 

Water   20  „ 

If  No.  2  is  used  more  washing  is  required. 

Lantern  Plates.  These  plates  are  suitable  for  reduction  in 
camera  or  contact  printing. 

Exposure.  It  is  impossible  to  give  any  correct  directions  on  this 
point,  as  the  quality  and  pressure  of  gas  varies  so  greatly,  while 
for  camera  work  the  light  is  subject  to  much  more  variation.  The 
brilliancy  and  vigour  of  the  slide  is  always  proportionate  to  the 
intensity  of  the  light.  As  a  guide  to  making  test  exposures  we 
give  the  following : — In  camera — mid«day,  sun  shining,  to  a 
north  light  with  stop  //16  from  30  to  60  sees.    Contact  printing 

467 


APPENDIX. 


requires,  with  a  No.  6  batswing  burner  and  a  negative  of  average 
density,  10  to  20  sees.,  at  a  distance  of  2  ft. 

Development.  This  should  be  conducted  in  a  temperature  of 
6o°  to  650  F.  The  process  should  be  continued  until  sufficient 
density  has  been  acquired.  This  may  be  judged  by  observing 
(1)  that  all  veil  has  disappeared  from  the  surface  of  the  plate ;  (2) 
that  the  image  is  clear  and  of  a  good  black  colour ;  (3)  that  the 
image  appears  dense  and  black  by  the  transmitted  light  of  the 
ruby  lamp.  Ifi  cases  of  under-  or  over-exposure  the  slide  will  be 
weak  or  flat.  Over-exposure  may  be  remedied  by  cutting  short 
the  development,  fixing,  washing,  and  re-developing  with  silver 
and  pyro.  The  plate  should  be  put  into  the  developer  without 
previous  wetting,  and  must  not  be  touched  or  brushed  on  its 
surface.    We  recommend  the  following  formula  : — 

Developer. 
No.  1. 

Hydrokinone  ...        ...       ..,       ...  ...  ...  160  grs. 

Sodium  sulphite                             ...  ...  ...  2  ozs. 

Citric  acid       ...       ...       ...       ...  ...  ...  60  grs. 

Potassium  bromide   40  „ 

Water                      ...       ...       ...  ...  ...  20  ozs. 

No.  2. 

Sodium  hydrate   100  grs. 

Water  ...       ...       ...       ...    ...     20  ozs. 

Take  equal  parts  of  each.  Should  No.  1  solution  become  yellow 
it  is  better  to  make  fresh. 

Fixing  Solutions. 
No.  r. 

Potassium  cyanide    5  oz. 

Water   10  ozs. 

Before  fixing  rinse  the  plate  well  under  the  tap,  and  after  immer- 
sion bring  out  into  the  light  and  wash  at  once  as  soon  as  all  the 
unaltered  silver  bromide  has  disappeared. 

No.  2. 

Sodium  hyposulphite    ...       ...       I  ozs. 

Water     20  „ 

If  No.  2  is  used  more  washing  is  required. 

468 


I.     PLATE-MAKERS'  FORMULAE. 

Re-developer. 
No.  i. 

Pyrogallic  acid    ...      io  grs. 

Citric  acid    25  „ 

Water     2  ozs. 

No.  2. 

Silver  nitrate   ...      20  grs. 

Distilled  water    ...       ...       ...       2  ozs. 

To  £  oz.  of  No.  1  add  30  drops  of  No.  2. 

Ilford  Plates— New  Developing  Formula. 

Stock  Solution. 

Pyrogallic  acid    ...       ...       1  oz. 

Water   ...       ...       ...       5.J  ozs. 

Add  20  drops  nitric  acid  before  the  pyro.  This  will  keep  for  a 
considerable  time. 

No.  1. 

Stock  solution   ...       ...       ...         I  to  2  ozs. 

Water  18  „ 

No.  2. 

Carbonate  of  soda  (crystals)  (not  bicarbonate)    ...      2  ozs.  av. 

Sulphite  of  soda        ...    ...      2   ,,  ,, 

Bromide  potassium    ...    ...  20  grs. 

Water  to        ...       ...       ...       ...    20  ozs. 

The  smaller  quantity  of  stock  solution  will  develop  softness  and 
detail  in  the  shadows  of  the  negative.  The  larger  quantity  is 
conducive  to  density  and  contrast  of  light  and  shade.  For  use 
take  equal  quantities  of  Nos.  1  and  2.  Pour  the  developer  care- 
fully over  the  plate,  avoiding  air  bubbles,  rock  the  dish,  carefully 
keeping  the  plate  well  covered  with  solution ;  allow  the  plate  to 
remain  after  all  detail  is  out,  to  obtain  proper  density.  Judge  of 
this  by  looking  through  the  plate.  To  compensate  for  errors  of 
exposure  the  proportions  of  Nos.  1  and  2  can  be  varied  thus ;  for 
under-exposure  use  more  of  No.  2  than  of  No.  1,  and  for  over- 
exposure more  of  No.  1  than  of  No.  2.  It  is  a  good  plan,  when 
there  is  a  doubt  as  to  the  exposure  being  correct,  to  commence 
the  development  with  twice  the  quantity  of  No.  1  to  that  of  No.  2, 
and  add  more  of  No.  2  if  found  desirable. 

469 


APPENDIX. 

Alum  Bath.  After  developing,  wash  the  plate  well  under  the 
tap,  and  immerse  for  a  few  minutes  in  Alum,  3  ozs. ;  Water, 
20  ozs. 

Fixing.  Wash  well  again,  and  fix  as  usual.  Hypo.,  1  lb. ; 
Water,  40  ozs.  Allow  to  remain  in  this  bath  for  several  minutes 
after  fixation  is  apparently  completed.  Never  omit  alum  bath, 
and  do  not  be  tempted  to  add  anything  either  to  it  or  to  the  fixing 
bath.  N.B. — This  developer  is  suitable  for  all  the  Ilford  negative 
plates,  and  yields  undoubtedly  the  finest  possible  results. 

A  Universal  Developer.  The  following  modifications  of  the 
Ilford  hydroquinone  formula  have  been  worked  out : — 


Or 


Hydroquinone... 
Bromide  potassium 
Sulphite  soda  ... 
Water,  up  to  ... 


Soda  hydrate 
Water  ... 


Hydroquinone... 
Eikonogen 
Potassium  bromide 
Sodium  sulphite 
Water,  up  to  ... 


Sodium  hydrate 
Water  


Solution  No.  1. 


Solution  No.  2. 


Solution  No.  I. 


Solution  No.  2. 


[60  grs. 

2  ozs.  av. 
20  „ 


100  grs. 
20  ozs. 


80  grs. 
120  „ 

30  » 

2  ozs. 
20  ,, 


100  grs. 
20  ozs. 


Use  as  follows : — For  negatives  on  Ilford  Plates — Equal  parts 
Nos.  1  and  2.  For  Ilford  Alpha  Lantern  Plates  (for  warm  tones) 
— One  part  No.  I,  half  part  No.  2,  two  parts  water.  For  Ilford 
Bromide  Papers — One  part  No.  1,  one  part  No.  2,  one  part 
water.  For  Ilford  Special  Lantern  Plates  (for  black  tones) — 
One  part  No.  1,  one  part  No.  2,  two  parts  water.  For  Ilford 
Alpha  Papers — One  part  No.  1,  half  part  No.  2,  two  parts  water. 
Although  it  must  be  understood  that,  in  our  opinion,  hydro 

470 


I.     PLATE-MAKERS  FORMUWE. 


quinone  is  somewhat  inferior  to  ferrous  oxalate  for  papers,  yet 
we  do  not  hesitate  to  put  forward  this  universal  developer  as  an 
alternative  method  of  working  for  those  who  desire  simplicity. 
The  mixed  hydroquinone  and  eikonogen  may  be  relied  on  for 
both  plates  and  papers.  Note. — The  clearing  bath  must  not  be 
used  when  developing  papers  with  this  developer. 

Imperial  Dry  Plate  Company's  Plates.— Developers. 

Pyro  and  Soda.  A. 
No.  i. 

Pyrogallic  acid      I  oz. 

Potassium  bromide    ...       ...       ...        ...        ...  50  grs. 

Soda  sulphite  ...        ...        ...        ...        ...        ...        5  ozs. 

Water  to       ,   ...    50 

No.  2. 

Soda  carbonate  (washing  soda)      ...    5  ozs. 

Water  to    ...    50  „ 

For  use  take  equal  quantities  of  No.  1  and  No.  2.  For  over- 
exposure use  more  of  No.  I.  For  under-exposure  use  more  of 
No.  2. 

Pyro  and  Metabisulphite.  B. 
Stock  Solution. 
Pyrogallic  acid  ...       ...       ...       ...       ...      1    oz.  av. 

Ammonium  bromide   »   M  „ 

Potassium  metabisulphite    ...       ...        ...       ...      1     „  _ 

Water  to  make      10  ozs. 

Dissolve  the  metabisulphite  and  bromide  in  part  of  the  distilled 
water  before  adding  the  pyrogallic  acid. 

No.  1. 

Stock  solution    l£  ozs. 

Distilled  water  to  make  altogether...       ...       ...    20  „ 

No.  2. 

Ammonia  ('890)    2\  drms. 

Water  ...       ...      20  ozs. 

For  use  take  equal  quantities  of  No.  1  and  No.  2.  For  over- 
exposure use  more  of  No.  1.  For  under-exposure  use  more  of 
No.  2. 

471 


APPENDIX. 

Pyro  and  Ammonia.  C. 
Stock  Solution. 

Pyrogallic  acid         ...       ...       ...  ...       ...      i  oz.  av. 

Ammonium  bromide  ...       ...       ...    I  „ 

Water  to  make         ...       ...       ...  ...       ...  10  ozs.  fluid. 

Sulphuric  acid,  strong    ...       ...  20  drops. 

No.  I. 

Stock  solution   i|  ozs 

Water     i8£  „ 

No.  2. 

Ammonia  ('890)        ...       ...       ...    i\  drms. 

Water  ...       ...       ...       ...       ...       ...       ...    20  ozs. 

For  use  take  equal  quantities  of  No.  1  and  No.  2.  For  over- 
exposure use  more  of  No.  1.  For  under-exposure  use  more  of 
No.  2. 

Hydroquinone.  D. 
No.  1. 

Hydroquinone  150  grs. 

Potassium  bromide    ...       ...       ...       ...       ...    25  „ 

Soda  sulphite  ...       ...       ...       ...       ...       ...     2  ozs.  av. 

Water  20  „  fluid. 

No.  2. 

Caustic  soda  100  grs. 

Water  20  ozs. 

For  use  take  equal  quantities  of  No.  1  and  No.  2.  For  over- 
exposure use  more  of  No.  1.  For  under-exposure  use  more  of 
No.  2. 

Oxalate  and  Iron.  E. 
No.  1. 

Potash  oxalate    4  ozs. 

Water   ...    16  „ 

No.  2. 

Iron  sulphate   4  ozs. 

Water   ...    12  „ 

Citric  acid   50  grs. 

For  developing  negatives  add  1  oz.  of  No.  2  to  3  ozs.  of  No,  1. 

472 


I.     PLATE-MAKERS'  FORMULAE. 

For  opals  add  i  oz.  of  No.  2  to  5  ozs.  of  No.  1 ;  and  to  every  oz. 
of  developer  add  about  10  drops  of  a  10  per  cent,  solution  of 
potassium  bromide.  No.  2  solution  must  always  be  added  to 
No.  1,  and  not  vice  versa. 

Eikonogen  Developer.  G. 
No.  1. 

Eikonogen      ...       ...    ...       ...       \  oz. 

Soda  sulphite   ...       ...    1  „ 

Water   ...       ...       ...       ...    20  ozs. 

No.  2. 

Caustic  potash    £  oz. 

Water  20  ozs. 

For  use  take  equal  parts  of  No.  1  and  No.  2.  For  over-exposure 
use  more  of  No.  1.    For  under-exposure  use  more  of  No.  2. 

Eikonogen  Developer.  H. 
In  one  Solution. 

Eikonogen    \  oz. 

Caustic  potash  ...       ...       ...       ...       ...       h  „ 

Soda  sulphite  ...       ...       ...       ...       ...       ...      I  „ 

Water  ...       ...       ...       ...       ...       ...       ...    20  ozs. 

Dilute  with  a  similar  volume  of  water.    If  the  picture  develops 

too  rapidly,  add  more  water. 

Metol.  I. 

Metol   75  grs. 

Soda  Sulphite ...    ...       ...  I  oz. 

Soda  carbonate  (washing  sod'i)      ...       ...       ...  2  ozs. 

Water   10  „ 

For  use  dilute  with  equal  measure  of  water. 

Metol.  J. 
No.  1. 

Metol  50  grs. 

Dissolve  in  water      ...       ...       ...       ...       ...    10  ozs. 

Then  add  soda  sulphite       ...       ...    1  oz. 

No.  2. 

Soda  carbonate  (washing  soda)      ...       ...       ...      2  czs. 

Water  to      10  , 

473 


APPENDIX. 
No.  3. 

Potassium  bromide     \  oz. 

Water  to        ...       ...    ...       ...    10  ozs. 

The  developer  for  normal  exposures  to  consist  of  3  parts  of  No.  1 
to  1  part  of  No.  2,  to  each  oz.  of  which  may,  as  a  rule,  be  added 
20  mins.  of  No.  3.  For  instantaneous  exposures  omit  No.  3,  for 
doubtful  or  tentative  development  use  10  mins.  of  No.  3  to  each 
oz.  of  developer. 

Amidol.  K. 

Amidol     \  oz. 

Soda  sulphite  ...    ...    2.\  ozs. 

Water     12  „ 

This  should  be  diluted  with  3  to  10  times  its  volume  of  water 
before  using.    N.B. — The  mixed  developer  will  not  keep. 

Clearing  Bath.  L. 

For  Negatives. 

Alum    ...       ...       ...       ...       ...       ...       ...     1  oz. 

Water  ...       ...       ...      10  ozs. 

Wash  before  and  after  immersing  in  alum  bath. 

For  Opals.  M. 

Alum    ...       ...       ...   ..       ...     2  ozs. 

Water  40  „ 

Citric  acid       ...       ...       ...       ...    \  oz. 

Or  instead  of  citric  acid  use  \  oz.  of  sulphuric  acid.  Do  not 
wash  before  immersing  in  clearing  bath. 

Fixing  Solutions. 
For  Glass  Negatives  and  Films.  N. 

Hypo   ...    1  lb. 

Water  50  ozs. 

For  Lantern  Plates,  Opals,  and  Bromide  Paper.  O. 

Hypo    ...    ...       ....       ...     4  ozs. 

Water   20  „ 

Bromide  Opals. — "Rapid"  for  Enlargement  and  "Slow" 
for  Contact  Printing.    The  exposure  required  with  "Slow" 

474 


I.    plate-makers'  formulae. 


opal  plates,  for  oxalate  developer  E,  for  contact  printing  with 
a  negative  of  ordinary  density,  will  be  about  ten  seconds,  at 
a  distance  of  12  inches  from  a  medium-sized  gas  burner  ;  for 
metol  developer  I  or  J,  about  five  seconds.  The  exposure 
required  with  "Rapid"  opal  plates,  for  oxalate  developer  E,  for 
contact  printing  with  a  negative  of  ordinary  density  will  be  about 
ten  seconds,  at  a  distance  of  24  inches  from  a  medium-sized  gas 
burner;  for  metol  developer  I  or  J  about  five  seconds.  For 
enlargements  use  the  test  paper  supplied  with  sizes  over 
8^  x  6|.  Metol  developer  I  is  strongly  recommended  for  opal 
work.  It  is  quicker  and  cleaner  than  oxalate  developer  E,  and 
does  not  require  the  clearing  bath  L.  With  oxalate  and  iron  E, 
add  1  oz.  of  No.  2  to  5  ozs.  of  No.  1,  and  to  every  ounce  of 
developer  add  about  10  drops  of  a  10  per  cent,  solution  of 
potassium  bromide.  No.  2  solution  must  always  be  added  to 
No.  1,  and  not  vice  versa.  When  development  is  complete, 
immerse  the  opal  in  clearing  solution  M,  for  a  few  minutes  before 
washing.  After  rinsing  ten  minutes  in  a  few  changes  of  water 
fix,  in  fixing  solution  O,  and  wash  as  usual.  Take  care  to  have 
everything  perfectly  clean.  The  slightest  trace  of  impurity  con- 
veyed to  the  solutions  by  dirty  hands  will  spoil  all  results. 
Observe  the  following : — Developing  solution  to  be  fresh  and 
cold.  Clearing  solution  immediately  after  development  before 
washing.  All  dishes  to  be  clean,  and  one  to  be  used  ex- 
clusively for  developing. 

Intensification  of  Negatives. 
No.  1. 

Potassium  bromide      ...    10  grs. 

Mercuric  chloride    ...       ...       ...    10  „ 

Water   1  oz. 

No.  2. 

Potassium  Cyanide    10  grs. 

Silver  nitrate    ...       ...       ...       ...       ...       ...  10  ,, 

Water   ...    I  oz. 

To  intensify  a  negative  soak  it  first  in  the  No.  1  solution  until 
more  or  less  bleached.  This  depends  on  the  amount  of  intensi- 
fication required.    After  a  thorough  washing  in  water  place  the 

475 


APPENDIX. 


negative  in  No.  2  solution  until  it  becomes  sufficiently  intense 
Instead  of  No.  2  solution  a  weak  solution  of  ammonia  may  be 
used,  or  a  10  per  cent,  solution  of  sulphite  of  soda.  Never 
intensify  a  negative  unless  absolutely  necessary,  for  unless  a 
great  amount  of  care  is  taken,  staining  is  almost  sure  to  occur. 

Uranium  Intensifier. 
In  one  Solution. 

Ferricyanide  of  potassium      ...    20  grs. 

Uranium  nitrate  ...       ...       ...       ...       ...  20 

Glacial  acetic  acid    I  drm. 

Water    ...    1  oz. 

Bathe  the  negative  in  this  solution  until  the  desired  density  is 
obtained,  and  afterwards  wash  well  in  water. 

Reducing  Negatives.  Wash  the  negative  well  in  water  and 
place  in  a  5  per  cent,  solution  (say  20  grs.  to  1  ounce  water)  of 
copper  chloride  until  the  surface  begins  to  appear  covered  with 
a  whitish  film.  It  should  then  be  taken  out  and  well  washed  in 
water,  and  then  placed  in  a  dilute  solution  of  ammonia,  when 
the  negative  will  become  clear  and  less  intense.  Instead  of 
ammonia,  hyposulphite  of  soda  fixing  bath  may  be  used,  when 
it  will  require  more  washing  than  with  ammonia.  Another 
method  recommended  by  Dr.  Eder  is  by  using  a  single  solution 
composed  as  follows  : — Ferricyanide  potassium  40  grs.  dissolved 
in  1  oz.  of  water.  (N)  Hyposulphite  soda  10  ozs.  In  this 
solution  the  negative  will  gradually  become  weaker,  and  when 
the  action  has  proceeded  far  enough  it  can  be  stopped.  Wash 
thoroughly  afterwards  in  water. 

Intensifying  and  Toning  Negatives. 
No.  1. 

Nitrate  of  uranium    1  oz. 

Glacial  acetic  acid    ...       ...       ...      1  ,, 

Water   50  „ 

No.  2. 

Ferricyanide  potassium                     ...       ..        ...  I  oz. 

Glacial  acetic  acid        ...      I  ,, 

Water    50  „ 

Soak  the  negative  first  in  solution  No.  I,  then  in  solution 
476 


I.     PLATE-MAKERS'  FORMULAE. 


No.  2.  The  result  will  be  a  fine  brown  tone.  Wash  thoroughly 
after  intensifying. 

Films.  These  films  are  coated  with  emulsion  (of  the  same 
rapidity  and  quality  as  used  for  Imperial  Plates),  on  thick 
transparent  celluloid,  consequently  requiring  the  same  ex- 
posure. They  can  be  used  in  ordinary  dark  slides  by  supporting 
the  frlm  with  a  thin  piece  of  card,  but  preferably  by  using  a  film 
carrier.  For  development,  any  of  the  imperial  plate  developing 
formulae  may  be  used,  but  it  is  not  advisable  to  develop  more 
than  one  film  in  a  dish,  so  preventing  all  risk  of  scratching  the 
moistened  emulsion  surface.  After  fixing  and  washing,  soak  the 
film  for  five  minutes  in  the  following:  — 

Glycerine    ...      I  oz. 

Water  25  ozs. 

After  ten  minutes'  washing,  in  running  water,  the  films  should  be 
hung  up  with  clips  to  dry. 

"  Special"  Lantern  Plates.  For  producing  transparencies  of  a 
black  tone.  The  exposure  required  for  a  negative  of  ordinary 
density  will  be  about  five  seconds,  at  a  distance  of  24  ins.  from  a 
medium-sized  gas  burner.  Developing  formula  (Hydroquinone) 
is  the  same  as  that  used  with  the  ordinary  plates.  See  D.  For 
development,  use  2  parts  of  No.  1  to  1  part  of  No.  2,  adding 
to  the  mixed  developer  an  equal  quantity  of  water.  Metol 
Developer  I  is  also  excellent.  After  development,  the  manipu- 
lations, washing,  etc.,  will  be  the  same  as  for  negatives,  but  use 
Fixing  Solution  O. 

"  Slow  "  Lantern  Plates.  For  producing  transparencies  of  a 
warm  tone.  The  exposure  required  for  a  negative  of  ordinary 
density  will  be  about  fifteen  seconds,  at  a  distance  of  12  ins. 
from  a  medium-sized  gas  burner.  Developing  formula  (Hydro- 
quinone) is  the  same  as  that  used  with  "  Special "  Lantern 
Plates,  excepting  that  equal  portions  of  Nos.  1  and  2  are  used 
adding  to  the  mixed  developer  an  equal  quantity  of  water. 

Lumiere's  Extra  Rapid  Gelatino-Bromide  of  Silver  Dry- 
Plates.  The  dark  room  should  be  lit  only  with  a  red  or  a  green 
light.  In  order  to  avoid  the  chances  of  fog,  artificial  light  should 
be  used  in  preference  to  natural  light,  as  the  intensity  of  the  latter 
varies  considerably  from  one  hour  to  another.   We  advise,  there- 

477 


APPENDIX 


fore,  tor  the  lighting  of  the  dark-room,  the  use  of  either  gas  or  a 
candle  in  a  lantern  having  two  yellow  and  two  green  glasses,  with 
a  movable  door  on  one  side,  arranged  in  such  a  way  as  to  enable 
half  of  these  glasses  to  be  suppressed,  leaving  one  green  and  one 
yellow  for  the  purpose  of  examining  the  negative  by  transmitted 
light.  Always  remove  the  dust  from  the  plate  with  a  soft  brush 
before  putting  it  into  the  developing  dish. 

Developers. 

Most  of  the  developers  usually  recommended  are  suitable  for 
the  development  of  Lumiere's  plates.  We  think  it  advisable, 
however,  to  mention  the  following  on  account  of  the  certainty 
which  the  operator  can  obtain  with  same,  provided  they  are 
used  always  at  a  temperature  of  6o°  to  650  F. 

Amidol. 

The  following  is  the  composition  of  the  normal  developer : — " 

Water   5  ozs.  or  100  parts. 

Sodium  sulphite  cryst.  pure   72  grs.  „      3  „ 

Amidol   12  „    „     0-5  „ 

This  solution  should  always  be  used  fresh.  In  order  to  use  the 
developer  in  the  most  economical  way,  it  is  recommended  to 
make  up  a  solution  of  sodium  sulphite  in  water  (which  will 
keep  for  any  length  of  time),  and  to  add  at  the  time  of  using  the 
necessary  amount  of  amidol,  either  weighed  or  measured  with  a 
small  horn  spoon. 

Pyro-Soda. 

Make  the  following  solutions  for  storage  and  use  : — 

A. 

Water    15  ozs. 

Sodium  sulphite    3 

Nitric  acid   30  mins. 

Pyro     ...       ...       ...       ...       ...   1  oz. 

B. 

Water  ...    15  ozs. 

Carbonate  soda  cryst.      4  „ 

Sodium  sulphite   ...  3 

478 


t.   plate-makers'  formula. 


To  develop  a  half-plate,  take : — 

Water  

Solution  A   

Solution  B 


I  oz. 
i  drm. 
i-ii  drms. 


Increase  the  quantity  of  B  drop  by  drop  during  development,  if  the 
negative  has  been  under-exposed.  For  portraiture  a  good  pyro- 
ammonia  developer  will  contain  in  each  ounce  of  developer  :— 

Pyrogallol,  with  sulphite  as  usual   I  gr, 

Potassium  bromide   \  „ 

Liquor  Ammoniae  (*88o)      ...    ...      2\  m!ns. 

This  will  allow  of  short  exposures.  When  the  image  has  attained 
the  desired  density,  stop  development  and  wash  ;  then  fix  in — 

Water     14  ozs.  or  1000  parts. 

Hyposulphite  of  soda    2   „    „    150  ,, 

In  very  warm  weather  or  in  hot  climates,  add  25  grs.  of  alum  dis- 
solved in  hot  water  and  filtered.  Afterwards  wash  the  negative 
in  running  water,  then  immerse  for  five  to  ten  minutes  in — 

Water   16  ozs.  or  1000  parts. 

Ordinary  Alum    I  oz.    ,,      60  ,, 

Washing  after  this  for  two  hours  in  water  changed  several  times 
will  usually  suffice.  It  is  better,  however,  to  continue  this  wash 
for  ten  to  twelve  hours  in  order  to  ensure  a  negative  which  will 
preserve  itself.  If  the  plate  shows  any  signs  of  frilli?ig,  soak 
before  fixing  in  a  saturated  solution  of  potash  alum,  wash  well, 
and  then  fix  as  above. 

Intensifying. 

If  the  negative  has  not  been  sufficiently  developed  and  the 
mage  is  wanting  in  vigour,  it  can  be  intensified  in  the  following 
bath  :— 

Water  ...   ;  1000  parts. 

Bichloride  of  mercury      6  ,, 

479 


APPENDIX. 


The  result  of  this  is  a  whitish  negative,  which  is  toned  by  putting 
the  plate,  after  having  washed  same,  in  the  following  solution : — 

Water  iooo  parts. 

Ammonia      40  „ 

Or : — To  1  pint  of  a  saturated  solution  of  mercury  bi- chloride 
add  1  drm.  of  commercial  hydrochloric  acid.  Bleach  well  and 
then  wash  thoroughly.  Then  soak  in  a  3  per  cent,  solution  of 
sodium  sulphite,  or  in  water  made  to  smell  strongly  with  liquor 
ammonias. 

Reducing. 

If  the  negative  is  too  dense,  it  can  be  reduced  as  follows. 
Prepare : — 

A. 

Water  500  parts. 

Red  prussiate  of  potash   5  w 

B. 

Water   50  parts. 

Hyposulphite  of  soda  ...       ...       ...       ...       5  » 

Mix  the  two  solutions  at  the  moment  of  using  them,  and  immerse 
all  at  once  the  negative  in  the  mixture,  the  action  of  which  is 
very  regular.  Wash  the  plate  again,  and  if  the  image  is  to  be 
retouched,  plunge  it  into  a  fresh  solution  of  borax  at  3  per  cent., 
then  dry. 

MawsOIl  &  Swan  recommend  the  following  developer  for  use 
with  their  "  Mawson"  and  "Castle"  Plates. 


Developer. 

Stock  Solution  (10  per  cent). 

Pyrogallic  acid   480  grs. 

Bromide  of  ammonium   240  „ 

Metabisulphite  of  potassium  480  „ 

Distilled  water  to  make    10  fluid  ozs. 

480 


I.     PLATE-MAKERS  FORMULAE. 

Dissolve  the  metabisulphite  in  part  of  the  water,  then  add  the 
other  ingredients,  and  make  up  to  bulk  with  water. 


Stock  solution     ...  300  mins. 

Distilled  water  to  make       ...    10  fluid  ozs. 

B. 

Liq.  Ammonia  (*88o)  ...       ...       ...       ...       ...    70  mins. 

Distilled  water  to  make       ...       ...       ...       ...    10  fluid  ozs. 

Use  equal  parts  of  A  and  B,  mix  at  time  of  developing. 

Pyro-Soda  Developer. 
A. 

Pyrogallic  acid  ...       ...       ...       .  .       ...    60  grs. 

Metabisulphite  of  potassium...       ...       ...       ...      5  ,, 

Distilled  water  to  make    10  fluid  ozs. 

B. 

Washing  soda ...    ...  ...  600  grs. 

Sulphite  of  soda        ...        ...        ...  ...  ...  800  „ 

Distilled  water  to  make    ...  ...    10  fluid  ozs. 

Use  equal  parts  of  A  and  B,  mixed  at  time  of  developing.  To 
correct  over-exposure  add  a  few  drops  of  10  per  cent,  solution  of 
potassium  bromide.    For  under-exposure,  increase  B  solution. 

Eikonogen  Developer. 
A. 

Eikonogen   100  grs. 

Sulphite  of  soda  (recryst.)  100  „ 

Distilled  water  to  make    ...       ...    10  fluid  ozs. 

B. 

Carbonate  of  potassium  (coml.)      ...   1200  grs. 

Sulphite  of  soda  (recryst.)  500  „ 

Distilled  water  to  make    10  fluid  ozs. 

c. 

Caustic  potassium  (sticks)   400  grs. 

Sulphite  of  soda  (recryst.)                       ...       ...  900 

Distilled  water  to  make       ...       ...       ...       ...  10  fluid  ozs. 

481  II 


APPENDIX. 

Three  parts  of  A  to  one  part  of  B.  In  cases  of  under-exposure, 
or  for  instantaneous  pictures,  use  C  instead  of  B.  To  correct 
over-exposure,  add  a  few  drops  of  10  per  cent,  solution  potassium 
bromide. 

Ferrous  Oxalate  Developer. 
The  following  solutions  may  be  made  in  quantity  and  kept 
separately : — 

A. 

Neutral  oxalate  of  potassium         ...   1200  grs. 

Bromide  of  potassium  ...       ...       ...       ...  5 

Citric  acid        ...        ...        ...    ...  15 

Distilled  water  to  make    10  fluid  ozs. 

B. 

Ferrous  sulphate   1600  grs. 

Citric  acid   120  M 

Distilled  water  to  make       ...        ...        ...        ...     10  fluid  ozs% 

Distilled  water  should  be  used,  otherwise  the  lime  in  ordinary 
water  will  cause  turbidity  frcm  formation  of  oxalate.  A  will 
keep  indefinitely,  but  B  should  not  be  used  after  it  turns  brown 
or  yellow.  When  required  for  use,  pour  four  parts  of  A  rapidly 
into  one  part  of  B.  The  resulting  solution  will  be  of  a  deep  red 
colour.  After  development  and  fixing,  the  plate  frequently  ex- 
hibits an  opalescent  appearance  ;  this  is  a  deposit  of  oxalate  of 
lime  that  forms  in  washing :  to  remove  it,  immerse  the  plate,  after 
thorough  washing  in 

Hydrochloric  acid    ...       ...       ...      I  oz. 

Saturated  sol.  alum  ...       ...       ...       ...       ...    19  ozs. 

washing  the  plate  again  after  the  operation. 

Hydrokinone  Developer. 
Ak 

Hydrokinone  40  grs. 

Metabisulphite  of  potassium...       ...       ...       ...    40  „ 

Distilled  water  to  make    10  fluid  ozs. 

B. 

Caustic  potassium  (sticks)   ...       ...       ...       ...    80  grs. 

Distilled  water  to  make    10  fluid  ozs. 

Use  equal  parts  of  A  and  B,  mixed  at  time  of  developing. 

482 


1.     PLATE-MAKERS  FORMULA. 


Fixing  Solution. 

Hyposulphite  of  soda   iooo  grs. 

Water  to  make    10  fluid  ozs. 

Developing  Solutions  recommended  for  Mawson  &  Swan's 
Photo-Mechanical  Plate. 

A 

Pyrogallic  acid 
Bromide  of  ammonium 
Metabisulphite  of  potassium... 
Distilled  water  to  make 

B. 

Liq.  Ammonia  (*88o) ...       ...       ...       ...       ...    70  mins. 

Distilled  water  to  make       ...        ...        ...        ...     10  fluid  ozs. 

Use  equal  parts  of  A  and  B,  mixed  at  time  of  developing.  If  the 
plate  has  been  correctly  exposed,  the  time  required  to  complete 
development  is  usually  from  four  to  six  minutes.  The  following 
developer  is  recommended  for  use  with  these  plates,  by  Mr. 
Wilkinson,  and  is  known  as 

Payne's  Hydroquinone  Developer. 
1. 

Hydroquinone... 
Metabisulphite  of  potash 
Bromide  of  potash 
Distilled  water 

2. 

Potassium  hydrate  (stick)    ...        ...        ...        ...    10  grs. 

Distilled  water  ...       ..        ...       ...       ...      1  oz. 

Equal  parts  of  1  and  2. 

Morgan  and  Kidd's  Richmond  Dry  Plates. 

Pyro  and  Ammonia  Developer. 
A. 

Citric  acid       ...       ...       ...       ...       ...       ...  1  dr. 

Sulphite  of  soda    4  ozs. 

Distilled  water         ...       ...       ...       ...       ...  60  ,, 

Pyrogallic  acid          ...        ...        ...    I  oz. 

Note.    Dissolve  the  citric  acid  and  the  sulphite  of  soda  in  the 

483 


30  grs. 
30  » 
30  » 

10  fluid  ozs. 


4  grs. 
4  M 
'  gr. 
I  oz. 


APPENDIX. 


water  before  adding  the  pyro  ;  keep  for  use  in  a  well-stoppered 
bottle. 

B. 

Liquid  ammonia  (  880)    I  oz. 

Bromide  of  ammonium        ...       ...    2  drs. 

Water  ...       ...       ...       ...       ...       ...       ...       2  ozs. 

C. 

Bromide  of  ammonium         ...       ...       ...       ...       2  drs. 

Water   ...       ...       ...       ...       2  ozs. 

Solutions  B  and  C  to  be  kept  in  dropping  bottles.  For  use  take 
of  A  solution  1  oz.,  water  3  ozs.,  B  solution  8  to  10  drops.  Add 
more  of  B  if  development  is  too  slow,  or  negative  is  undertimed. 
For  over-exposure  add  a  few  drops  of  C  and  more  A  solution. 
For  under-exposure  add  more  of  B  solution,  should  image  appear 
to  be  developing  up  too  dense,  dilute  developer  with  water  and' 
continue  development  until  all  detail  is  out. 

Pyro  and  Soda  Developer. 
A  and  C  solutions  as  above. 

.  B. 

Water   60  ozs. 

Pure  dry  carbonate  of  soda   4  „ 

For  use  take  equal  parts  of  A  and  B.  If  more  density  is  required 
use  a  drop  or  two  of  C  to  each  ounce  of  mixed  developer.  For 
over-exposure  add  a  few  drops  of  C  and  more  A  solution.  For 
under-exposure  add  more  B  solution,  and  dilute  with  water  if 
negative  is  developing  with  too  much  density.  After  develop- 
ment wash  and  then  soak  for  5  minutes  in  a  saturated  solution  of 
common  alum,  wash  again  and  fix  in  hyposulphite  of  soda,  8  ozs. 
to  a  quart  of  water. 

The  Paget  Prize  Plate  Co.  "  Phoenix  XXX  and  XXXXX." 

Instructions  for  use. — Keeping.  Plates  should  be  kept  in  a  cool 
place,  in  as  pure  air  as  possible,  and  dry.  But  damp  is  not  so 
injurious  as  excessive  heat.  They  should  be  stored,  if  possible, 
in  a  room  where  gas  is  not  burnt.  If  circumstances  necessitate 
their  being  kept  in  an  impure  atmosphere,  each  package  should 

484 


I.    plate-makers'  formula. 


be  wrapped  in  a  double  coating  of  tin  or  lead  foil ;  this  is  an 
effectual  protection. 

Development.  Any  developer  may  be  used  with  these  plates, 
but  for  quality  of  result,  gradation,  and  adaptability  to  varieties 
of  subject  and  circumstance,  there  is  none  equal  to  pyro  and 
ammonia.  The  following  formula  has  been  carefully  adapted  to 
suit  these  plates,  and  we  strongly  recommend  its  use  in  pre- 
ference to  any  other  : — 

Stock  Solutions. 
P. 

Pyrogallic  acid          ...       ...       ...       ...  ...       i  oz. 

Citric  acid                           ...       ...       ...  ...  60  grs. 

Sodium  sulphite  (pure)                             ...  ...  2 \  ozs. 

Distilled  water  to  make       ...       ...       ...  ...  20  ,, 

A. 

Liquid  ammonia  (*88o)        ...       ...       ...       ...       1  oz. 

Ammonium  bromide   ...        ...      80  grs. 

(For  Phoenix  Plates,  120  grs.) 
Distilled  water  to  make    20  ozs. 

Dissolve  the  citric  acid  and  sulphite  in  about  half  the  water, 
which  may  be  made  hot  to  assist  the  solution.  When  cold  add 
the  pyro,  and  make  up  to  20  ozs.  with  remainder  of  water. 
This  solution  will  keep  a  long  time,  if  preserved  from  contact 
with  the  air,  in  well-stoppered  bottles.  Sulphite  of  soda  (not 
sulpha  or  sulphzVfc)  varies  greatly  in  quality,  and  spoils  if  left 
long  exposed  to  the  air.  The  best  re-crystallised  should  be 
used. 

Studio  developer.  Dilute  1  part  of  P  with  5  parts  of  water, 
and  dilute  1  part  of  A  with  5  parts  of  water.  Mix  the  two  dilute 
solutions  in  equal  quantities  for  use.  (Such  developer  contains 
about  2  grs.  pyro,  2  mins.  ammonia,  \  gr.  bromide,  5  grs.  sulphite, 
\  gr.  citric  acid,  in  each  ounce.)  If  a  thinner  and  softer  negative 
be  desired,  use  less  of  P. 

Outdoor  work.  For  groups,  street  scenes,  near  views,  and 
other  subjects  not  too  distant  and  with  moderate  contrasts,  the 
above  developer  will  generally  be  found  suitable  ;  but  the  outdoor 
photographer  who  wishes  to  be  able  to  modify  his  developer  to 

485 


APPENDIX. 


suit  great  varieties  of  subjects  will  probably  prefer  three  separate 
stock  solutions,  each  of  10  per  cent,  strength,  as  follows  : — 

No. 

Pyrogallic  acid   

Sodium  sulphite 
Citric  acid 

Distilled  water  to  make 

No.  2. 

Ammonia  bromide     ...    ...       ...       i  oz. 

Distilled  water  to  make    9  ozs.  55  mins. 

No.  3. 

Liquid  ammonia  ('880)        ...       ...       ...       ...       1  ox. 

Distilled  water  to  make    10  ozs. 

Ten  minims  of  each  of  these  solutions  will  contain  1  gr.  pyro, 
1  gr.  bromide,  and  1  min.  of  liquid  ammonia  *88o  respectively. 
To  the  inexperienced  photographer  it  may  be  useful  to  point  out 
that  the  strength  of  developer  to  be  used  depends  greatly  on  the 
natural  contrasts  of  light  and  shade  in  the  subject ;  in  a  distant 
view,  for  instance,  there  is  usually  very  little  contrast;  in  a 
portrait  or  near  view,  with  foliage,  etc.,  the  contrasts  are  fre- 
quently great.  As  a  general  rule,  the  less  contrast  in  the  subject 
the  stronger  should  be  the  developer.  In  ordinary  cases  this 
will  vary  from,  say,  1  or  i|  gr.  of  pyro  per  ounce  for  a  strongly 
lighted  portrait,  to  as  much  as  6  or  even  8  grs.  per  ounce  for  a 
distant  landscape  or  marine  view.  Bromide  may  vary  from  one- 
sixth  up  to  an  amount  equal  to  weight  of  pyro  used.  The 
quantity  of  bromide  chiefly  influences  the  time  of  development ; 
if  much  be  used  a  longer  time  will  be  required.  If  the  developer 
be  necessarily  a  strong  one,  a  large  proportion  of  bromide  should 
be  used,  and  plenty  of  time  given.  In  most  cases  the  quantity 
of  ammonia  should  not  much  exceed  that  of  pyro ;  it  is  generally 
advisable  to  commence  development  with  only  about  half  or 
two-thirds  of  the  ammonia,  and  add  the  remainder  as  may  be 
found  necessary. 

Over-exposure.  A  solution  of  citrate  of  soda,  1  oz.  in  10  ozs. 
of  water,  is  a  most  useful  one.  If  over-exposure  be  known  or 
suspected,  commence  with  a  developer  containing  less  than 

486 


...       1  oz. 

2\  OZS. 

60  grs. 
9  ozs.  55  mins. 


I.     PLATE-MAKERS'  FORMULAE. 


usual  of  ammonia.  This  will  cause  the  image  to  come  out  more 
slowly,  and  give  more  time  to  observe  its  character.  When 
nearly  all  necessary  details  are  just  visible,  if  the  appearance  of 
the  image  be  such  as  to  indicate  over-exposure,  at  once  add  to 
the  developer  some  of  the  citrate  solution,  the  quantity  required 
depending  on  the  amount  of  over-exposure,  and  varying  from  a 
few  drops  to  2  or  3  drms.  This  will  stop  development,  but  not 
intensification — i.e.,  no  more  detail  will  be  produced,  but  the 
image  already  formed  will  be  allowed  to  grow  stronger.  To 
obtain  the  requisite  density  more  of  either  P  or  A,  or  both,  may 
be  now  added,  and  the  action  allowed  to  proceed  as  usual.  If 
too  much  citrate  has  been  added,  the  developer  may  be  poured 
off,  the  plate  washed,  and  a  fresh  less-restrained  developer  ap- 
plied. Citrate  possesses  this  great  advantage  over  bromide, 
which  is  generally  used  for  the  same  purpose  :  that  whereas 
bromide  destroys  the  latent  image,  citrate  does  not,  but  only 
restrains  development  so  long  as  itself  is  present. 

For  Under-exposure,  use  developer  containing  P  and  A  in 
equal  quantities,  but  strong.  No  plate  much  under-exposed  ever 
gives  a  thoroughly  satisfactory  result ;  if  at  all  possible  expose 
another,  and  for  all  subjects  requiring  very  brief  exposure  use  the 
most  rapid  plates. 

General  Hints.  Do  not  wet  the  plate  before  development. 
Do  not  drop  plate  into  developer.  Do  not  use  pyro  developer 
for  a  second  plate.  Lay  the  dry  plate  in  dry  dish  and  pour 
developer  over  it  in  one  sweep,  taking  care  plate  is  well  covered. 
Rock  dish  occasionally  during  development ;  this  has  a  great 
influence  on  vigour.  However  "safe"  you  may  consider  your 
light,  do  not  expose  plate  to  it  more  than  is  absolutely  necessary. 
Have  a  cover  for  dish  during  development.  Do  not  fix  plate 
directly  you  see  enough  detail,  but  give  enough  time  to  acquire 
density  also.  Fix  thoroughly.  Have  all  your  solutions  and 
washing  water  as  nearly  at  the  same  temperature  as  possible, 
and  under  6o°  if  you  can ;  differences  of  temperature  tend  to 
produce  frilling  ;  warm  developer  induces  fog  and  flatness  ;  very 
cold  developer  takes  a  long  time  to  act,  and  may  be  used 
stronger. 

Fixing.    Wash  well  after  development,  and  fix  in — 

Hyposulphite  of  soda ...        ...        ...        ...       ...       6  ozs. 

Water   ,,,       1  pt. 

487 


APPENDIX. 


The  plate  should  remain  in  the  fixing  bath  for  several  minutes 
after  it  appears  to  be  cleared.  When  fixed,  it  should  be  placed, 
after  a  good  washing,  in  a  saturated  or  nearly  saturated  solution 
of  common  alum,  and  left  for  three  or  four  minutes.  This  greatly 
assists  in  extracting  the  hypo,  and  in  every  way  improves  the 
plate.  It  should  then  be  very  thoroughly  washed  with  water, 
and  allowed  to  dry  spontaneously.  On  no  account  must  it  be 
heated  to  hasten  drying.  In  very  hot  weather  the  alum  bath  may 
be  used  before  fixing,  as  an  extra  precaution  against  frilling.  Do 
not  expose  the  plate  to  white  light  until  it  has  been  placed  in  the 
alum  after  fixing. 

Intensification.  With  proper  exposure  and  development  in- 
tensification ought  never  to  be  necessary.  The  following 
intensifier  is,  however,  very  effectual : — 

M. 

Bichloride  of  mercury  (corrosive  sublimate)        ...  \  oz. 

Bromide  of  potassium  ...       ...    \  „ 

Distilled  water  ...       ...       ...       ...       ...  I  pt. 

S. 

Cyanide  of  potassium  (in  crystals  or  best  fused)  ...  \  oz. 
Water   I  pt. 

Drop  a  strong  solution  of  nitrate  of  silver  into  this  (S),  stirring 
round  and  adding  silver  until  a  precipitate  is  formed  which  does  not 
re-dissolve.  Do  not  use  for  twenty-four  hours.  Soak  the  plate, 
after  fixing  and  thorough  washing,  in  the  alum  bath  for  at  least 
ten  minutes,  wash  thoroughly  for  at  least  half  an  hour,  and  lay  it 
in  solution  M  until  it  becomes  white  all  over  and  has  the  ap- 
pearance of  a  positive.  Then  wash  thoroughly,  say  for  an  hour, 
and  place  in  solution  S  until  it  becomes  perfectly  black  all 
through.  Wash  once  more,  and  allow  to  dry.  A  plate  so  treated 
should  be  absolutely  black,  with  clear  shadows ;  and  if  the 
soaking  in  alum  and  washing  after  each  operation  have  been 
thoroughly  done,  there  is  little  to  fear  with  regard  to  permanency. 
The  least  trace  of  yellowness  indicates  that  the  washing  has  not 
been  effectually  carried  out.  If  the  amount  of  intensification 
required  be  not  great,  a  10  per  cent,  solution  of  sulphite  of  soda 
may  be  used  instead  of  solution  S.  If  sulphite  be  used  the 
washing  after  M  need  not  be  prolonged. 

488 


I.    plate-makers'  formulae. 


Reduction.  In  cases  where,  from  over-development,  the 
negative  has  been  allowed  to  become  too  dense,  the  following 
method  of  reducing  (due  to  Mr.  E.  Howard  Farmer)  will  be 
found  very  convenient  and  effective : — Prepare  a  solution  of 
ferricyanide  of  potassium  (red  prussiate  of  potash)  by  dissolving 
i  oz.  in  a  pint  of  water,  and  keep  for  use  when  required.  To 
reduce  a  negative,  immerse  it  in  a  hypo  solution  of  a  strength  of 
about  i  oz.  to  the  pint  of  water  (a  little  of  the  fixing  bath  diluted 
answers  perfectly),  to  which  has  been  added  a  little  of  the  above 
ferricyanide  solution.  A  gradual  uniform  reduction  will  take 
place,  the  rapidity  depending  on  the  quantity  of  ferricyanide 
added.  When  sufficiently  reduced,  take  out  and  wash  thoroughly. 
To  reduce  locally,  immerse  the  plate  in  water  for  a  few  minutes, 
and  apply  the  mixed  solution  with  a  camel's-hair  brush  or  pellet 
of  cotton  wool  to  the  parts  required.  The  ferricyanide  solution 
must  be  added  to  the  hypo  when  required,  as  the  mixed  solution 
does  not  keep.  Pyro-soda,  hydrokinone,  or  eikonogen  may  be 
used,  if  preferred,  with  these  plates. 

Pyro-Soda. 
No.  i. 

Pyrogallic  acid  ...       ...    ...         \  oz. 

Sulphuric  acid     ...       5  drops. 

Distilled  water  to  make    20  ozs. 

No.  2. 

Carbonate  of  soda  (crystals,  pure)  ... 

Sulphite  of  soda  (pure)   

Distilled  water  to  make 
Equal  parts  of  each. 

Hydrokinone. 
No.  1. 

Hydrokinone  ... 
Methylated  spirit 
Sulphurous  acid 
Potassium  bromide 

Dissolve  the  hydrokinone  in  the  spirit,  and  add  the  acid.  In 
another  vessel  dissolve  the  potassium  bromide  in  3  ozs.  of 

489 


2  ozs. 

2  n 
20  „ 


IO  ozs. 
2  oz. 


j 


APPENDIX. 

distilled  water.  Mix  the  two  solutions,  and  make  up  to  20  ozs. 
with  distilled  water. 

No.  2. 


Caustic  soda  (in  sticks) 
Sodium  sulphite 
Distilled  water  to  make 

1  part  of  each  to  4  parts  of  water, 
hard  a  negative,  use  more  water. 


  ...       1  oz. 

  5 ozs- 

  20  „ 

If  this  be  found  to  give  too 


Eikonogen. 
No.  1. 

Eikonogen       ...       ...       ...    1  oz. 

Sodium  sulphite        ...       ...    1^  ozs. 

Potassium  bromide                         ...       ...       ...  8  grs. 

Distilled  water  to  make       ...       ...       ...       ...  30  ozs.' 

60  grs.  hydrokinone  added  to  above  is  a  decided  improvement, 
increasing  brilliancy  and  density. 

No.  2. 

Potassium  carbonate  ...       ...       ...       ...       ...       1  oz. 

Distilled  water  to  make       ...       ...       ..,       ...      10  ozs. 

3  parts  of  No.  1  to  1  part  of  No.  2. 

Lantern  Plates.   Instructions  for  Use. 

Rapid  Series. 

Exposure.  These  plates,  which  give  only  black  tones,  require 
about  one-sixth  of  the  exposure  of  the  slow  series  as  below. 

Development.  Any  of  the  formulae  given  for  the  slow  series 
for  black  tones  are  equally  suitable  for  these. 

Slow  Series. 

The  great  difference  in  density  and  character  of  negatives 
renders  it  impossible  to  make  any  definite  statements  with  regard 
to  exposure.  The  "slow"  plates,  exposed  in  contact  with  a 
good,  clear  landscape  negative  of  average  density,  have  been 
found  to  require  for  black  tones  an  exposure  of  about  30 
seconds  at   a  distance  of  1  foot  from  an  ordinary  fishtail 

•  490 


I.     PLATE-MAKERS'  FORMULA. 


gas-flame,  or  i  inch  of  magnesium  wire  burnt  at  a  distance  of 
3  feet.  The  exposures  given  under  the  heading  of  "  warm  tones  " 
also  refer  to  the  same  negative.  Denser  negatives  will,  of  course, 
require  more.  In  the  case  of  negatives  of  different  densities, 
it  is  better  to  regulate  the  exposure  by  varying  the  distance  from 
the  light  than  by  altering  the  time.  Dense  negatives  being 
exposed  nearer  to,  and  thin  ones  farther  from,  the  light. 

Development.  For  black  tones  development  should  in  no 
case  exceed  3  minutes.  If  longer  is  required  the  exposure  has 
been  insufficient,  and  the  result  will  not  be  so  good.  Any  of 
the  following  formulae  are  suitable : — 


Hydrokinone  ... 
Sulphurous  acid 
Potassium  bromide 
Water  to 


Hydrokinone. 
Solution  1. 


\  oz. 

*  n 

60  grs. 
20  ozs. 


Solution  2. 

Caustic  soda                        ...       ...       ...       ...  £  oz. 

Sodium  sulphite                                      ...       ...  2\  ozs. 

Water  to    20  „ 

For  use,  take  ^  oz.  of  each  to  1  oz.  of  water. 


Eikonogen  Developer. 
Solution  i. 

Eikonogen                           ...       ...       ...  ...  £  oz. 

Sodium  sulphite        ...   '    ...       ...       ...  ...  \\o/.s. 

Potassium  bromide    ...                            ...  ...  S   grs.  • 

Distilled  water  to      ...       ...       ...       ...  ...  30  ozs. 


Solution  2. 

Potassium  carbonate  ...       ...       ...       ...       ...        1  oz. 

Distilled  water  to      ...       ...       ...       ...       ...      10  ozs. 

Take  3  parts  of  No.  1  to  1  part  of  No.  2  solution. 

491 


APPENDIX. 


Rodinal  Developer. 


Rodinal  concentrated  solution 
Water  


I  part. 
30  parts. 


This  is  a  very  clean  developer,  and  gives  a  rich  black  colour. 


Ferrous  Oxalate  Developer. 
Solution  1. 


Neutral  oxalate  of  potash 
Citric  acid 

Hot  water   


16  ozs. 
60  grs. 
50  ozs. 


Proto-sulphate  of  iron 

Citric  acid   

Hot  water   


Solution  2. 


4  ozs. 
15  grs. 
8  ozs. 


Bromide  of  potassium 
Water  


Solution  3. 


Joz. 
10  ozs. 


For  development,  take  6  ozs.  of  No.  1,  and  add  1  oz.  of  No.  2 
and  24  drops  of  No.  3.    Gives  cold  black  tones. 


Pyrogallic  acid 
Sodium  sulphite 
Citric  acid 
Distilled  water  to 


Pyro-Ammonia. 
Solution  1. 


I  oz. 
l£  ozs. 
i  oz. 
10  ozs. 


Liquor  ammonia  (*88o) 
Ammonium  bromide  ... 
Distilled  water  to 


Solution  2. 


1  oz. 


10  ozs. 


For  use,  take  45  minims  of  each  solution  and  make  up  with 
water  to  2  ozs. 

492 


I.    plate-makers'  FORMULA. 
Warm  Tones  Developer. 


Solution  i. 

Hydroquinone          ...    ...       ...  ^  oz. 

Sulphurous  acid        ...    ...       ...  £  ,, 

Potassium  bromide    ...        ...        ...  ...        ...  60  grs. 

Water  to    20  ozs. 

Solution  2. 

Caustic  soda    ...       ...       ...       ...  ...       ...  I  oz. 

Sodium  sulphite        ...        ...        ...  ...        ...  2  A  ozs. 

Water  to    20  ., 

Solution  3. 

Bromide  of  ammonia  ...       ...       ...  ...       ...  1  oz. 

Carbonate  of  ammonium      ...       ...    I  „ 

Water  to        ...       ...       ...       ...  ...       ...  20  ozs. 


Carbonate  of  ammonium  should  be  in  clear  lumps ;  if  from 
exposure  to  the  air  it  has  become  coated  with  the  white  powdery 
bicarbonate,  the  latter  should  be  scraped  off. 

Brown.    Exposure,  60  seconds,   1  foot  from  gas-flame,  or 

2  inches  of  magnesium  wire  burnt  at  a  distance  of  3  feet 
Developer,  solution  1,  £  oz. ;  solution  2,  £  oz.  ;  solution  3, 
100  minims;  water  to  2  ozs.  Time  required  in  development, 
about  5  minutes. 

Purple  brown.  Exposure,  90  seconds,  1  foot  from  gas-tlame, 
or  3  inches  of  magnesium  wire  burnt  at  a  distance  of  3  feet. 
Developer,  solution  1,  £  oz.  ;  solution  2,  £  oz.  ;  solution  3,  200 
mins  ;  water  to  2  ozs.  Time  required  in  development,  about 
10  minutes. 

Purple.    Exposure,    3  minutes,   1   foot  from   gas-flame,  or 

3  inches  of  magnesium  wire  burnt  at  a  distance  of  2  feet. 
Developer,  solution  1,  \  oz. ;  solution  2,  \  oz.  ;  solution  3, 
250  mins. ;  water  to  2  ozs.  Time  required  in  development, 
about  12  minutes. 

Red.  Exposure,  5  minutes  1  foot  from  gas-flame,  or  5  inches 
of  magnesium  wire  burnt  at  a  distance  of  2  feet.  Developer, 
solution  1,  A  oz.  ;  solution  2,  \  oz  :  solution  3,  300  mins.  ; 
water  to  2  ozs.  Time  required  in  development,  about  15 
minutes. 


493 


APPENDIX. 


Wash  the  plate  in  running  water  for  at  least  3  minutes 
before  fixing :  otherwise  a  yellow  stain  may  afterwards  appear. 

Fixing-Bath. 

The  simplest  is  the  following  : — 

Hyposulphite  of  soda  ...       ...       ...       ...       6  ozs. 

Water   20  „ 

After  fixing,  the  transparency  is  well  washed  for  1  hour  in  several 
complete  changes  of  water. 

Printing-Out  Opals. — Instructions  for  Use.  Printing  is  best 
done  in  the  special  frame,  in  which  the  negative  is  fixed  to  the 
frame  and  the  opal  to  the  back  in  such  a  way  that  the  opal  can 
be  examined  during  printing  and  afterwards  returned  to  exact 
register  on  negative.  If  an  ordinary  frame  be  used  the  negative 
must  be  firmly  secured  in  its  place,  say  by  small  wood  wedges 
or  other  means  found  convenient.  In  laying  the  opal  down  it 
should  be  pushed  thoroughly  up  into  one  corner  of  the  frame, 
so  that  after  examination,  during  printing,  it  may  be  replaced  in 
exactly  the  same  position  without  difficulty.  Printing  should  be 
carried  on  to  the  same  extent  as  when  printing  paper.  Somewhat 
deeper  printing  is  required  when  the  "  combined  "  bath  is  used 
than  is  necessary  for  separate  toning  with  sulphocyanide.  It 
should  be  borne  in  mind,  when  toning,  that  the  finished  image 
will  be  bluer  and  slightly  stronger  when  dry  than  in  the  wet 
state. 

Toning.  Either  of  the  following  well-known  baths  answers 
admirably. 

Combined  Toning  and  Fixing  Bath. 
No.  1  Stock. 

Hyposulphite  of  soda  ...    ...      20  ozs. 

Alum  (potash  alum  only)     ...    5  „ 

Sodium  sulphate  (not  sulphite)    14  „ 

Water  to    I  gallon. 

Dissolve  the  hypo  and  alum  each  in  about  1  quart  of  hot  water, 
mix,  and  then  add  sodium  sulphate  already  dissolved,  making 
up  to  1  gallon  with  remainder  of  water.  This  mixture  should 
then  be  left  for  some  hours  for  the  precipitate  to  settle,  when 

494 


I.   plate-makers'  formulae. 


the  clear  solution  may  be  poured  off  or  filtered  and  is  then  ready 
for  use.    It  will  keep  indefinitely. 

No.  2  Stock. 

Gold  chloride   15  grs. 

Acetate  of  lead         ...       ...       ...       ...       ...  64 

Distilled  water    8  ozs. 

Dissolve  the  acetate  of  lead  in  the  water  and  add  the  gold.  A 
heavy  precipitate  forms  in  this  solution,  which  should  be  shaken 
up  when  any  is  to  be  poured  out :  it  redissolves  when  added  to 
No.  1  stock  solution.  For  use  :  mix  8  ozs.  of  No.  1  with  1  oz.  of 
No.  2.  When  this  bath  is  used  the  plates  should  not  be  washed 
before  toning. 

Separate  Toning  Bath. 

Sulphocyanide  of  ammonium         ..        ...       ...      30  grs. 

Gold  chloride   ...       ...       ...       2$  „ 

Water   16  ozs. 

Before  immersion  in  this  toning  bath,  the  plates  should  be  very 
thoroughly  washed  for  at  least  15  minutes  in  running  water. 
This  is  necessary  to  insure  even  toning.  In  hot  weather,  if 
necessary,  the  plates  may  be  soaked  in  alum  (alum  4  ozs.,  water 
20  ozs.)  for  five  minutes  before  toning  in  this  bath.  Another 
thorough  washing  is  necessary  between  the  alum  and  toning 
baths. 

Fixing  Bath. 

Hyposulphite  of  soda  ...       ...    3  ozs. 

Water   I  pint. 

With  most  negatives  the  most  pleasing  result  will  be  obtained 
by  vignetting  or  masking  the  edges.  If  by  any  accident  any  part 
of  the  edge  be  printed  where  not  intended,  the  film  may  be 
removed  by  careful  rubbing  with  a  warm  damp  rag,  or  (on  the 
polished  surface  opals  only)  by  scraping  with  a  sharp  knife. 

Clearing  Stains. 

The  extreme  edges  of  these  plates  sometimes  become  brown, 
and  after  very  long  keeping  this  stain  may  extend  more  or  less 
inwards.    In  any  case  the  discoloration  does  no  harm  whatever, 

495 


APPENDIX. 


as,  after  the  picture  is  finished,  it  may  be  easily  wiped  away 
with  a  tuft  of  cotton-wool  dipped  in  a  deep  solution  of  cyanide 
of  potassium  oz.  in  a  pint  of  water).  As  this  solution  also 
reduces  the  image,  it  must  be  carefully  used,  and  water  should 
be  kept  running  over  the  picture  during  the  operation,  so  as 
to  avoid  a  sharp  line.  The  same  solution,  diluted  with  five  or 
ten  times  its  bulk  of  water,  and  poured  all  over  the  picture, 
forms  an  admirable  clearer  or  reducer,  should  such  be  required. 
Note.    Cyanide  of  potassium  is  extremely  poisonous. 

Bromide  Opals. — Instructions  for  use.  Exposure.  The  time 
required  for  exposure  will,  of  course,  vary  with  the  light  and 
the  density  of  the  negative.  As  a  guide,  however,  it  might  be 
stated,  that  a  negative  of  good  silver  printing  qualities  required 
an  exposure  of  ten  seconds  at  a  distance  of  one  foot  from  an 
ordinary  fish-tail  burner,  or  half  an  inch  of  magnesium  wire 
burnt  at  a  distance  of  four  feet  from  the  negative. 

Development.  For  black  tones  the  following  developer  is  the 
one  chiefly  used : — 

Ferrous  Oxalate  Developer. 
Solution  i. 

Neutral  oxalate  of  potash    16  ozs. 

Citric  acid    60  grs. 

Hot  water    50  ozs. 

Solution  2. 

Protosulphate  of  iron     4  ozs. 

Citric  acid  (or  acetic  acid  \  drm.)   \  02. 

Hot  water    8  ozs. 

Solution  3. 

Bromide  of  potassium    \  oz. 

Water   10  ozs. 

For  development,  take  (when  cold)  6  ozs.  of  No.  1,  and  add  1  oz. 
of  No.  2,  and  \  drm.  of  No.  3.  For  warm  black  tones  use  the 
hydrokinone  developer,  made  up  as  follows: — 

496 


I.  plate-makers'  FORMULA. 


Hydrokinone  Developer. 
Solution  i. 

Hydrokinone  ... 

Sulphurous  acid        ...  ...   

Potassium  bromide  ... 
Water  to   


Solution  2. 

Caustic  soda   ^  oz. 

Sodium  sulphite        ...       ...       ...       ...       ...  2 A  ozs. 

Water  to        ...       ...        ...    50  ozs. 


For  use  take  equal  parts  of  the  two  solutions.  By  increasing 
the  exposure  and  using  less  of  No.  1  solution,  still  browner  images 
can  be  obtained.  Other  developers,  such  as  Eikonogen,  Pyro, 
Rodinal,  etc.,  can  also  be  used. 

Clearmg. — When  using  the  ferrous  oxalate  developer  it  is 
necessary,  as  soon  as  development  is  completed,  to  at  once 
immerse  the  opal  in  either  of  the  following  baths  : — 


Water  ...       ...       ...    80  ozs. 

Alum  (powder)      ...       2  „ 

Citric  acid       ...        ...        ...        ...        ...        ...        1  oz. 

or 

Acetic  acid      ...       ...       ...       ...    I  drm. 

Water   20  ozs. 


Use  just  enough  to  cover  the  opal,  allow  it  to  act  for  a  minute  or 
so,  then  pour  it  away  and  apply  a  fresh  portion.  Well  rinse  in 
clean  water  and  place  in  the  fixing  bath  composed  of 

Fixing  Bath. 

Hyposulphite  of  soda ...       ...       ...       ...       ...       4  ozs. 

Water   ...       ...       ...       ...       ...     20  „ 

In  this  the  opal  should  remain  for  ten  or  fifteen  minutes,  after 
which  they  are  well  washed  and  dried. 

Notes. — To  insure  success  the  utmost  cleanliness  should  be 
observed,  especially  with  the  Ferrous  Oxalate  Developer,  with 

497  K^ 


*oz. 
1 

f  tt 
60  grs. 
50  ozs. 


APPENDIX. 


which  a  dish  should  be  kept  for  each  operation  and  used  for  that 
only.  The  clearing  bath  is  only  necessary  with  the  Ferrous 
Oxalate  Developer ;  do  not  wash  before  immersing  the  opal  in 
it.  With  the  Hydrokinone  Developer  the  plate  must  be 
thoroughly  rinsed  before  fixing,  otherwise  yellow  stains  will 
appear. 

Printing-out  Lantern  Plates. — Instructions  for  use.  Printing 
may  be  done  in  an  ordinary  frame,  half  of  the  back  being 
opened,  as  is  usual  with  printing  paper.  The  progress  of 
printing  is  best  judged  by  reflected  light,  and  should  be  carried 
on  until  the  densest  parts  of  the  negative  (which  should  be  clear 
glass  in  the  finished  transparency)  begin  slightly  to  print.  It 
must  be  borne  in  mind  that  the  density  of  an  image  to  be  seen 
by  transmitted  light  requires  to  be  much  stronger,  and  therefore 
more  fully  printed  than  in  the  case  of  paper.  As  the  slightest 
want  of  sharpness  in  a  lantern  slide  is  greatly  magnified  on  the 
screen,  the  plate  should,  under  no  circumstances,  be  removed 
from  the  negative  until  completely  printed ;  unless  a  frame 
specially  made  for  the  purpose  is  used.  Print  by  direct  sunlight 
when  possible ;  and  as,  in  order  to  ensure  the  greatest  possible 
sharpness,  it  is  desirable  that  the  light  always  fall  at  the  same 
angle  on  the  negative,  the  frame,  after  being  examined,  should 
be  replaced  in  the  same  position  as  before.  To  prevent  mistakes, 
mark  one  side  of  frame  "  top,"  and  keep  it  so.  When  using  a 
frame  larger  than  the  negative,  it  is  necessary  to  adopt  some 
means  of  preventing  extraneous  light  from  reaching  the  edges  of 
the  lantern  plate.  A  mask  will  answer  the  purpose  ;  but  it  must, 
of  course,  be  put  on  the  back  of  the  negative  (not  the  film  side). 

Toning. — Either  of  the  following  well-known  baths  answers 
admirably : — 

Combined  Toning  and  Fixing  Bath. 
No.  1  Stock. 

Hyposulphite  of  soda           ...       ...       ...       ...  20  ozs. 

Alum  (potash  alum  only)    5  oz. 

Sodium  sulphate  (not  sulphite)    14  ozs. 

Water  to                                              ...       ...  I  gal. 


Dissolve  the  hypo  and  alum  each  in  about  a  quart  of  hot  water, 

498 


i.    PLATE-MAKERS'  FORMULAS. 


mix,  and  then  add  sodium  sulphate  already  dissolved,  making 
up  to  a  gallon  with  remainder  of  water.  This  mixture  should 
then  be  left  for  some  hours  for  the  precipitate  to  settle,  when 
the  clear  solution  may  be  poured  off  or  filtered,  and  is  then  ready 
for  use.    It  will  keep  indefinitely. 

No.  2  Stock. 

Gold  chloride  ...        ...        ...        ...        ...        ...  15  grs. 

Acetate  of  lead          ...       ...       ...    64 

Water  (distilled)    8  ozs. 

Dissolve  the  acetate  of  lead  in  the  water  and  add  the  gold.  A 
heavy  precipitate  forms  in  this  solution,  which  should  be  shaken 
up  when  any  is  to  be  poured  out  ;  it  redissolves  when  added  to 
No.  1  stock  solution.  For  use :  Mix  8  ozs.  of  No.  1  with  1  oz.  of 
No.  2.  With  this  bath  the  plates  should  be  rather  more  fully 
printed  than  when  separately  toned.  They  should  not  be  washed 
before  toning. 

Separate  Toning  Bath. 

Sulpho-cyanide  of  ammonium        ...       ...       ...      30  grs. 

Gold  chloride  ...    ...       ...       ...       2\  „ 

Water   ...        ...      16  ozs. 

Before  immersion  in  this  toning  bath  the  plates  should  be  very 
thoroughly  washed  for  at  least  fifteen  minutes  in  running  water. 
This  is  necessary  to  ensure  even  toning.  In  hot  weather,  if 
necessary,  the  plate  may  be  soaked  in  alum  (alum  4  ozs.,  water 
20  ozs.)  for  five  minutes  before  toning  in  this  bath.  Another 
thorough  washing  is  necessary  between  the  alum  and  toning 
baths.  The  image  is  a  transparency,  which  has  to  be  toned 
right  through,  of  course  takes  longer  than  a  paper  print,  which 
is  toned  on  the  surface  only,  and  the  colour  should  only  be 
judged  by  transmitted  light. 

Fixing  Bath. 

Hyposulphite  of  soda  ...    ...       3  ozs. 

Water   I  pint. 

499 


APPENDIX. 


Verel  &  Co.'s  "  Runaway  "  and  other  Plates. 

Pyro-Soda  Developer. 
Stock  Pyro  Solution. 

Pyrogallic  acid  .. .        ...       ...    i  oz. 

Nitric  acid         ...        ...       ...        ...        ...       ...    20  drops. 

Water    ...    ...       ...      6  ozs. 

No.  I. 

Stock    ...       ...       ...       ...       ...     2  ozs. 

Water  18  „ 

No.  2. 

Carbonate  soda  (crystals) 
Carbonate  potash 
Sulphite  soda  ... 
Bromide  Potash 
Water   

Use  in  equal  parts. 

Pyro-Ammonia  Developer. 
No.  1. 

Pyrogallic  acid 
Sulphite  soda  ... 
Citric  acid 

Water    

No.  2. 

  ...         ...  oz. 

  4  dnns. 

  16  ozs. 

For  half-plate,  use  2  drms.  each  of  above  in  2  ozs.  of  water. 
Should  the  plate  be  over-exposed,  add  a  few  drops  of  a  solution 
of  bromide  of  ammonium  (equal  parts  of  bromide  and  water), 
and  use  a  smaller  quantity  of  No.  1, — say  3  parts  of  No.  2  to 
1  of  No  1 . 

Alum  Bath. — One  part  of  alum  to  20  parts  of  water.  Leave 
in  this  bath  for  10  minutes.  You  should  always  use  the  alum 
bath. 

Fixing. — Hyposulphite  of  soda,  1  to  4  parts  of  water. 
500 


2  ozs. 

1  It 

2  „ 

80  grs. 
20  ozs. 


I  oz. 

£  drm. 
16  ozs. 


Liquor  ammonia 
Ammonium  bromide  ... 
Water  


t,     PLATE-MAKERS'  FORMULAS. 


Eastman's  "Permanent"  and  "Extra  Rapid'  Bromide 
Papers. 

Oxalate  Developer. 
No.  i. 

Oxalate  of  potash  (neutral)   lib. 

Hot  water   48  ozs. 

No.  2. 

Proto-sulphate  of  iron           ...  ...  ...        ...  1  lb. 

Citric  acid        ...       ...       ...  ...  ...       ...  £  oz. 

Hot  water                             ...  ...    32  ozs. 

No.  3. 

Bromide  potassium     ...       ...       ...       ...       ...      1  drm^ 

Water   ...       ...       ...    10  ozs. 

These  solutions  keep  separately,  but  must  be  mixed  only  for 
immediate  use. 

To  Develop. 

For  Normal  Exposures. — Take  in  a  suitable  tray  No.  1,  6  ozs. ; 
No.  2,  1  oz. ;  No.  3,  \  drm.  (about  5  drops  to  the  ounce  of 
developer).  These  solutions  should  be  employed  as  cool  as 
possible,  and  mixed  in  the  order  named.  After  exposure,  soak 
the  paper  in  water  until  limp ;  then  immerse  in  the  developer. 
Use  fresh  developer  for  each  batch  of  prints.  With  a  glass- 
bottomed  tray,  8  ozs.  of  developer  are  sufficient  for  a  25  X  30 
print.  The  bromide  is  added  to  the  developer  for  the  purpose 
of  producing  vigorous  contrasts  of  light  and  shade  and  of  pre- 
serving the  clear  whites  of  the  prints.  When  printing  from  a 
negative  which  is  thin,  or  flat,  the  proportion  may  be  safely 
increased  to  twice  that  named  above. 

No  Toning  required. — With  Eastman's  permanent  or  extra 
rapid  bromide  paper  the  final  tones  may  be  varied  to  almost 
any  extent,  depending  as  they  do  upon  the  density  of  the 
negative,  the  quality  of  light  used  in  printing,  and  the  proportion 
of  iron  and  bromide  employed  in  the  developer.  For  delicate, 
grey  tones  like  the  India-ink  washes  of  an  artist's  brush,  it  is 
requisite  to  expose  to  a  well-diffused  light,  and  to  develop  with 
a  smaller  quantity  of  iron  and  bromide  in  the  developer.  For 

501 


APPENDIX. 


vigorous  prints,  with  full  contrasts,  the  image  should  appear 
slowly  and  should  develop  up  strong,  clear,  and  brilliant.  When 
the  shadows  are  sufficiently  black,  pour  off  the  developer  and 
flood  the  print  with  the  clearing  solution  : 

Acetic  acid    ...      i  drm. 

Water    ...       ...       ...       ...       ...       ...       ...    32  ozs. 

Instead  of  acetic  acid,  citric  acid  may  be  used  in  the  clearing 
solution,  in  the  proportion  of  £  ounce  to  the  quart  of  water. 
Citric  acid  has  the  advantage  of  being  odourless. 

Purpose  of  Clearing  Solution. — The  purpose  of  the  clearing 
solution  is  to  prevent  the  precipitation  of  the  iron  from  the 
developer  into  the  fibre  of  the  paper.  This  can  only  be  done  by 
keeping  the  paper  acid  while  washing  out  the  developer.  Do 
not  wash  the  print  after  pouring  off  the  developer,  and  before 
applying  the  clearing  solution.  Use  a  sufficient  quantity  to  flow 
over  the  print,  say  2  ozs.  for  an  8  X  10.  Allow  it  to  act  for 
one  minute,  and  then  pour  it  off  and  apply  a  fresh  portion  ; 
repeat  the  operation  a  third  time,  then  rinse  in  four  changes 
of  pure  water  and  immerse  for  ten  minutes  in  the  fixing  bath  : 

Hyposulphite  of  soda  ...       ...       ...       ...       ...     4  ozs. 

Water  20  „ 

After  fixing,  wash  thoroughly  in  several  changes  of  water  for 
two  hours  at  least,  and  hang  up  to  dry. 

Solio  Paper  (Printing-out  Paper). 

Caution.  This  paper  being  more  sensitive  to  light  than  ordinary 
albumenised  paper,  great  care  must  be  taken  to  handle  it  in  a 
subdued  light  only.  Whilst  printing,  the  prints  should  be 
examined  in  a  weak  light,  otherwise  a  great  risk  will  be  incurred 
of  destroying  the  high  lights  and  purity  of  the  resulting  picture. 
The  paper  must  also  be  kept  perfectly  dry. 

Printing  should  be  done  in  a  strong  light  if  the  negatives 
are  hard;  only  thin  or  delicate  negatives  being  printed  in  the 
shade.  The  printing  should  be  carried  only  a  little  darker  than 
it  is  desired  the  finished  print  should  appear,  as  this  paper  loses 
very  little  in  the  subsequent  toning  and  fixing  operations.  It  is 
advisable  to  use  a  piece  of  waterproof  material  in  the  back  of 
the  printing  frame  during  damp  weather. 

Toning.  Any  of  the  usual  formulae  may  be  used  for  this 
502 


I.     PLATE-MAKERS'  FORMULA. 


paper,  but  the  following  are  specially  recommended  as  giving  by 
far  the  best  results  : — 

Eastman's  Combined  Toning  and  Fixing  Bath. 
Stock  Solution  A. 

Hyposulphite  of  soda...        ...        ...    8  ozs. 

Alum  (common)        ...       ...       ...       ...       ...       6  n 

Water   80  „ 

When  dissolved  add  borax,  2  ozs.  ;  dissolved  in  hot  water,  8  ozs. 
Let  it  stand  overnight  and  decant  the  clear  liquid. 

Stock  Solution  B. 

Chloride  of  gold      ...  15  grs. 

Acetate  of  lead  (sugar  of  lead)    64  „ 

»    Water  ...    ...    8  ozs. 

Solution  B  should  be  shaken  up  before  using,  and  not  filtered. 
For  use  take  stock  solution  A,  8  parts  ;  stock  solution  B,  1  part. 
Place  prints,  without  previous  washing,  into  the  above.  The 
combined  bath  must  be  cold,  not  above  400  or  500  F.  This 
condition  can  be  obtained  by  placing  a  piece  of  ice  in  the  bath 
when  toning.  If  your  bath  is  too  warm  you  will  get  yellow 
prints,  with  a  greenish  cast  in  the  half  tones.  Use  a  ther- 
mometer, and  keep  it  in  your  toning  bath  all  the  time.  The 
combined  bath  is  an  acid  solution,  any  attempt  to  neutralise  the 
bath  will  precipitate  the  alum.  Tone  to  desired  colour,  and 
immerse  prints  for  five  minutes  in  the  following  salt  solution  to 
stop  the  toning  : — 

Salt    1  oz. 

Water   ...     32  ozs. 

If  the  prints  tone  in  less  than  fifteen  minutes  it  is  desirable  that 
the  following  extra  fixing  bath  be  used  to  ensure  thorough  fixing. 
After  the  salt  bath  give  one  change  of  cold  water  and  fix  for  ten 
minutes  in  the — 

Extra  Fixing  Bath. 

Hyposulphite  of  soda                     ...       ...       ...  1  oz. 

Sulphite  of  soda  (crystals)                                 ...  60  grs. 

Borax     $  oz. 

Water  ...        20  ozs. 

503 


APPENDIX. 


Wash  one  hour  in  running  cold  water,  or  in  sixteen  changes  of 
cold  water,  when  prints  may  be  mounted  same  as  albumen  prints. 

Examining  prints  while  toning.  Tone  to  the  colour  desired 
in  finished  prints.  Great  care  must  be  taken  not  to  tone  too 
many  prints  with  the  same  bath.  Nine  ounces  of  the  mixed 
toning  bath,  made  as  above  formula,  will  tone  one  sheet  of 
paper  of  the  standard  size,  i\\  by  17  inches,  or  one  is.  packet, 
and  more  should  not  be  used. 

Printing  from  hard  negatives.  The  combined  bath  makes 
soft  prints,  and  may  be  used  to  advantage  with  hard  or  under- 
timed  negatives. 


Separate  Toning  Baths — Sulphocyanide  Bath. 

Cold  Tones.  Owing  to  the  softening  action  of  sulphocyanide 
on  gelatine  it  is  necessary  to  pass  the  prints  through  an  alum 
bath  previous  to  toning.  After  the  prints  have  been  washed  in 
three  changes  of  water  they  should  be  immersed  in  the  following 
bath  for  ten  minutes  : — 

Alum    ...       ...       ...       ...    ...       \  oz. 

Water  ...    ...       ...     20  ozs. 

Thoroughly  wash  after  the  alum  bath  for  five  minutes  in  running 
water. 

Toning  Bath. 

Stock  Solution  A. 

Sodium  acetate         ...       ...    ...    600  grs. 

Water  ...        20  ozs. 

Gold  chloride   15  grs. 

Stock  solution  B. 

Ammonium  sulphocyanide   50  grs. 

Water   ...     20  ozs. 

For  use:  Take  of  A,  2  parts;  B,  2  parts;  water,  4  parts. 
Allow  to  stand  an  hour  before  using.  The  toning  may  be  stopped 

5°4 


I.     PLATE-MAKERS*  FORMULAE. 

at  any  stage  by  transferring  the  prints  to  the  following  (the 
prints  must  be  kept  in  motion  for  the  first  few  seconds) : — 

Short  Stop. 

Common  salt   ...    I  oz. 

Water   32  ozs. 

The  prints  should  be  well  washed  and  then  fixed  in  the 
following 

Fixing  Bath. 

Sodium  hyposulphite   ...       3  ozs. 

Sodium  sulphite        ...       ...       ...    U „ 

Water   20  ,. 

After  the  prints  are  fixed  they  should  be  washed  for  one  hour  in 
running  water. 

Alum  bath  can  be  used  before  or  after  fixing  if  desirable, 
care  being  taken  to  well  wash  the  prints  between  each  two 
operations. 

Warm  Tones.  Wash  the  prints  from  five  to  ten  minutes,  then 
immerse  in  either  of  the  following  baths,  examining  the  prints  by 
transmitted  light : — 

Platinum  Toning  Bath  (for  Sepia  Tones). 

Stock  Solution. 

Potassium  chloro-platinite  ...    5  grs. 

Citric  acid      ...       ...  40  ,, 

Sodium  chloride  (salt)      40  ,, 

Water   ...    ...  20  ozs. 

Tone  to  a  dark  brown  or  chocolate  colour  (not  to  a  black). 

Acetate  Bath  (Brown  Tones). 

Stock  Solution. 

Sodium  acetate         ...       ...    ...    150  grs. 

Gold  chloride  ...       ...       ...       ...       ...       ...  5 

Water  ...       ...       ...    ...      40  ozs. 

Tone  to  a  chestnut  brown  only.  Short  stop  and  fixing  operations 
are  the  same  as  for  sulphocyanide  bath. 

505 


APPENDIX. 


Black  Tones.  Exquisite  black  purple,  and  blue-black  tones 
can  be  obtained  by  using  the  following  combinations  of  toning 
baths : — Tone  the  prints  in  platinum  or  acetate  bath,  as  per  above 
formulae,  until  they  just  begin  to  assume  a  chestnut  brown  ;  then 
transfer  at  once  to  the  combined  toning  and  fixing  bath,  and  tone 
to  the  desired  colour.  By  the  above  process  the  acetate  bath 
yields  blue-black  and  purple  tones.  The  platinum  bath  yields 
brown-black  tones. 

Note.  In  all  the  above  operations  care  must  be  taken  to  keep 
the  prints  moving  in  the  various  solutions. 

Caution.  With  the  separate  toning  and  fixing  baths  the 
greatest  care  must  be  taken  not  to  allow  any  sodium  hyposulphite 
to  come  in  contact  with  the  prints  while  in  the  toning. 

Washing.  The  prints  can  be  most  effectually  washed  after 
fixing  by  removing  them  from  one  dish  to  another,  repeatedly 
changing  the  water.  The  process  of  washing  should  not  exceed 
one  hour. 

Drying.  The  prints  can  be  dried  by  laying  them  upon  blotting 
paper  face  upward,  but  must  not  be  left  between  blotting  paper  ; 
or  they  may  be  suspended  by  one  corner  and  allowed  to  dry 
spontaneously. 

Glazed  surface.  This  may  be  obtained  by  squeegeeing  the 
prints  as  soon  as  they  are  taken  from  the  last  washing  water 
face  downward  on  to  a  ferrotype  plate,  the  surface  of  which  has 
been  previously  polished  with  waxing  solution  as  follows  : — 

Spermaceti  wax        ...       ...       ...       ...       ...    120  grs. 

Benzine  ...       ...       ...       ...       ...       ...     20  ozs.  ' 

Enamelled  surface.  For  a  highly  enamelled  surface  a  piece 
of  plate  glass  must  be  used  instead  of  the  ferrotype  plate.  A 
little  of  the  solution  should  be  applied  to  the  ferrotype  or  glass 
plate  by  means  of  a  tuft  of  cotton  wool,  going  over  the  whole 
surface  and  then  polishing  off  thoroughly  with  a  soft  cloth. 
French  chalk  may  be  used  instead  of  waxing  solution  for  the 
glass  plate,  but  it  should  be  used  in  the  same  manner.  The 
prints  should  be  taken  from  the  water  and  laid  face  downward 
on  to  the  polished  surface — or  a  better  method  is  to  float  them 
on  to  the  glass  under  water — a  piece  of  American  or  india-rubber 
cloth  being  then  placed  on  the  prints.  They  should  be  squeegeed 

506 


t.     PLATE-MAKERS  FORMULAE. 


well  into  contact  to  expel  all  water  and  air  bubbles.  The  plate 
should  then  be  placed  on  end,  and  the  print  allowed  to  dry 
thoroughly,  before  any  attempt  is  made  to  strip  them. 

Matt  surface.  A  dead  matt  surface  can  be  obtained  by  using 
in  place  of  the  ferrotype  or  glass  plate  a  piece  of  finely-ground 
glass  or  celluloid. 

Opalines.  When  making  opalines,  the  alum  bath  previously 
mentioned  for  hardening  the  gelatine  film  should  on  no  account 
be  used,  as  it  will  prevent  perfect  adhesion.  The  combined 
bath  is  unsuitable  for  making  opalines. 

Note.  The  hot  gelatine  bath  should  not  be  used  for  solio 
paper ;  the  prints  will  adhere  perfectly  if  squeegeed  on  to  the 
glass  directly  they  are  taken  from  the  washing  water. 

Burnishing.  The  temperature  of  the  burnisher  should  not 
exceed  170°  Should  a  bar  burnisher  be  used  the  surface  of  the 
prints  must  be  lubricated.  This  is  best  done  by  using  a  piece  of 
ordinary  Castile  soap  as  follows  : — The  soap  should  be  rubbed 
with  a  piece  of  flannel  or  cloth  until  it  makes  the  cloth  greasy ; 
the  surface  of  the  print  is  then  rubbed  over  with  the  cloth.  If, 
on  the  other  hand,  roller  burnishers  are  used,  it  is  not  necessary 
to  lubricate  the  prints. 

Mounting.  The  prints  may  be  mounted  with  starch  paste  in 
the  ordinary  manner,  but  if  it  be  desired  to  mount  them  with  an 
enamelled  surface,  the  prints  should  first  be  backed  with  backing 
paper,  then  brushed  over  with  very  thin,  pure,  well-filtered  glue 
and  placed  in  position  on  the  mount.  Any  chemically  pure 
paper  will  answer  the  purpose  for  backing  prints. 

Note.  When  mounting  a  quantity  of  prints  in  the  ordinary 
way  it  is  usual  to  place  them  in  a  pile,  after  being  taken  from 
the  water,  one  on  the  other,  for  the  purpose  of  pasting  the  backs. 
It  is  not  safe  to  do  this  with  solio  paper,  unless  the  prints  have 
been  previously  passed  through  an  aluin  bath  before  or  after  fixing. 

Nikko  Paper. 
Oxalate  Developer. 
No.  1. 

Oxalate  of  potash      ...    ...       ...  lib. 

Hot  water    ...    ...     48  ozs. 

Acetic  acid      ...       ...       ...       ...    3  drms. 

507 


APPENDIX. 


No.  2. 

Proto-sulphate  of  iron  ...  ...        ...        ...        i  lb. 

Hot  water      ...       ...       ...    ...  32  ozs. 

Acetic  acid  (or  citric  acid,  |  oz.)    \  drm. 

No.  3. 

Bromide  potassium    ...       ...       ...       ...       ...       1  oz. 

Water  ...    I  quart. 

These  solutions  keep  separately,  but  must  be  mixed  only  for 
immediate  use.  To  develop,  take  in  a  suitable  tray  :  No.  Ij  6  ozs. ; 
No.  2,  1  oz. ;  No.  3,  \  drm.  Mix  in  the  order  given  ;  use  cold. 
After  exposure,  soak  the  paper  in  water  until  limp  ;  then  immerse 
in  the  developer.  The  image  should  appear  slowly,  and  should 
develop  up  strong,  clear,  and  brilliant.  When  the  shadows  are 
sufficiently  black  pour  off  the  developer  and  flood  the  print  with 
the 

Clearing  Solution. 

Acetic  acid    I  drm. 

Water  ...       ...       ...    ...       ...      32  ozs. 

Do  not  wash  the  print  after  pouring  off  the  developer  and  before 
applying  the  clearing  solution.  Use  a  sufficient  quantity  to  flow 
over  the  print,  say  2  ozs.  for  an  8  in.  by  10  in.  Allow  it  to  act 
for  one  minute,  and  then  pour  it  off  and  apply  a  fresh  portion  ; 
repeat  the  operation  a  third  time,  then  rinse  in  pure  water  and 
immerse  for  ten  minutes  in  the 

Fixing  Bath. 

Hyposulphite  of  soda    3  ozs. 

Water   16  „ 

After  fixing,  wash  thoroughly  for  two  hours  and  hang  up  to  dry. 
Use  fresh  developer  for  each  batch  of  prints.  With  a  glass 
bottom  tray  7  ozs.  of  developer  are  sufficient  for  a  25  in.  by  30  in. 
print. 

No  toning  required.  WTith  Eastman's  Nikko  paper  the  finest 
tones  are  obtained  entirely  by  development,  and  range  from  a 
soft  grey  to  a  rich  velvety  black,  depending  somewhat  upon  the 
density  of  the  negative  and  the  quality  of  the  light  used  in  printing. 

508 


I.     PLATE-MAKERS'  FORMULAE. 


Clean  dishes. — Clean  hands.  The  faintest  trace  of  hyposulphite 
of  soda  or  of  pyrogallic  acid  is  fatal  to  good  results  with  Nikko 
paper,  and  the  operator  cannot  be  too  careful  to  avoid  any  con- 
tamination. The  tray  used  for  developing  with  oxalate  should 
never  be  used  for  anything  else. 

To  avoid  yellow  prints  four  things  are  absolutely  necessary. 
First,  the  developer  must  be  acid  ;  second,  the  clearing  solution 
must  be  used  as  directed  ;  third,  fresh  hypo  solution  is  required 
for  fixing  each  batch  of  prints ;  fourth,  the  washing  must  be 
thorough  after  fixing.  Mealy  prints  are  caused  by  over-exposure, 
alkaline  oxalate,  or  too  little  iron  ;  and  are  never  the  fault  of  the 
paper. 

Other  developers — Metol,  Amidol,  Eikonogen,  Hydrochinone, 
and  Para-amidophenol — may  all  be  used  to  develop  Eastman's 
Nikko  paper,  formulee  for  the  use  of  which  accompany  the 
chemicals. 

Platino-Bromide  Paper. 
An  argentic  bromide  paper  giving  platinum  effect. 

Oxalate  Developer. 
No.  i. 

Potassium  oxalate  (neutral)  ... 
Hot  water 

No.  2. 

Ferrous  sulphate       ...    ...       i  lb. 

Citric  acid      ...       ...       |  oz. 

Hot  water    ...       ...      32  ozs. 

No.  3. 

Potassium  bromide    ...       ...       ...       ...       ...       1  drm. 

Water     10  ozs. 

These  solutions  must  be  cooled  and  kept  separately,  and  should 
be  mixed  only  for  immediate  use. 

To  develop.  For  normal  exposures  take  in  a  suitable  tray 
No.  1,  6  ozs.  ;  No.  2,  1  oz.  ;  No.  3,  \  drm.  (about  5  drops  to  the 
ounce  of  developer).  These  solutions  should  be  employed  as 
cool  as  possible,  and  mixed  in  the  order  named.    After  exposure, 

5°9 


1  lb. 

48  ozs. 


APPENDIX. 


soak  the  paper  in  water  until  limp  ;  run  off  the  water,  and  pour 
the  developer  rapidly  and  evenly  over  the  sensitive  surface.  Use 
fresh  developer  for  each  batch  of  prints.  With  a  glass-bottomed 
tray  8  ozs.  of  developer  are  sufficient  for  a  25  in.  by  30  in.  print. 
The  bromide  is  added  to  the  developer  for  the  purpose  of  pro- 
ducing vigorous  contrasts  of  light  and  shade,  and  of  preserving 
the  clear  whites  of  the  prints.  When  printing  from  a  negative 
which  is  thin  or  flat,  the  proportion  may  be  safely  increased  to 
twice  that  named  above  ;  whereas  in  the  case  of  a  hard  negative 
it  may  be  reduced,  or  entirely  omitted.  The  image  should  appear 
slowly,  and  should  develop  up  strong,  clear,  and  brilliant ;  with 
a  fine  black  tone.  For  delicate  grey  tones,  like  the  India-ink 
washes  of  an  artist's  brush,  it  is  requisite  to  expose  to  a  well- 
diffused  light,  and  to  develop  with  a  smaller  quantity  of  iron  and 
bromide  solution  in  the  developer.  When  the  shadows  are 
sufficiently  black  pour  off  the  developer  and  flood  the  print 
with  the 

Clearing  Solution. 

Acetic  acid    1  drm. 

Water   32  ozs. 

Instead  of  acetic,  citric  acid  may  be  used  in  the  clearing  solution, 
in  the  proportion  of  |  oz.  to  the  quart  of  water.  Citric  acid  has 
the  advantage  of  being  odourless.  Do  not  wash  the  print  after 
pouring  off  the  developer  and  before  applying  the  clearing 
solution. 

Purpose  of  clearing  solution.  The  purpose  of  the  clearing 
solution  is  to  prevent  the  precipitation  of  the  iron  from  the  de- 
veloper into  the  fibre  of  the  paper.  This  can  only  be  done  by 
keeping  the  paper  acid  while  washing  out  the  developer.  Use  a 
sufficient  quantity  to  flow  over  the  print,  say  2  ozs.  for  an  8  in. 
by  10  in.  Allow  it  to  act  for  one  minute,  pour  it  off,  and  apply 
a  fresh  portion  ;  repeat  the  operation  a  third  time,  then  rinse  in 
four  changes  of  pure  water  and  immerse  for  ten  minutes  in  the 

Fixing  Bath. 

Sodium  hyposulphite   ...       ...       ...       4  ozs. 

Water   20  „ 

After  fixing,  wash  thoroughly  in  several  changes  of  water  for  two 
hours  at  least,  and  hang  up  to  dry. 

510 


I.   plate-makers'  formulae. 


Alum  bath.  If  it  be  desired  to  toughen  the  gelatine  of  the 
fixed  print,  the  latter  may  be  immersed  in  a  saturated  alum  bath 
after  removal  from  the  fixing  bath,  care  being  taken  to  thoroughly 
rinse  between  the  two  operations.  In  all  cases  a  thorough  washing 
must  complete  the  process. 

Blisters.  In  very  warm  weather,  and  in  tropical  climates 
generally,  blisters  sometimes  appear  in  Platino-Bromide  paper. 
These  may  usually  be  avoided  by  adding  a  little  common  salt  to 
the  first  washing  water  used  after  fixing.  Obstinate  cases  of 
blistering  may  be  cured  by  adding  a  small  quantity  of  ice  to  the 
solution  in  which  they  appear.  The  paper,  too,  should  not  be 
roughly  handled,  as  the  abrasion  caused  thereby  induces  blistering. 

Clean  dishes. — Clea?i  hands.  The  faintest  trace  of  sodium 
hyposulphite  or  of  pyrogallic  acid  is  fatal  to  good  results  with 
Platino-Bromide  paper,  and  the  operator  cannot  be  too  careful 
to  avoid  contamination.  The  tray  used  for  developing  with 
oxalate  should  never  be  used  for  anything  else. 

To  avoid  yellow  prints  four  things  are  absolutely  necessary. 
First,  the  developer  must  be  acid;  second,  the  clearing  solution 
must  be  used  as  directed  ;  third,  fresh  hypo  solution  is  required 
for  fixing  each  batch  of  prints ;  fourth,  the  washing  after  fixing 
must  be  thorough.  Mealy  prints  are  caused  by  over  exposure, 
alkaline  oxalate,  or  too  little  iron,  and  are  never  the  fault  of  the 
paper. 

Othe?  developers.  Metol,  Amidol,  Eikonogen,  Hydrochinone, 
and  Para-amidophenol  may  all  be  used  to  develop  Eastman's 
Platino-Bromide  paper.  Formulae  for  the  use  of  these  chemicals 
are  provided  with  them.  Of  the  above  developers,  Metol  is 
specially  recommended,  as  under  : 

Water   80  ozs. 

Sodium  sulphite        ...        ...    2  „ 

Metol   160  grs. 

Sodium  carbonate      ...    \\  czs. 

Dissolve  in  the~order  named.  Develop  in  the  usual  way,  but 
avoid  removing  the  print  from  the  bath  until  quite  developed,  as 
a  repeated  exposure  to  the  air  during  development  has  a  tendency 
to  yellow  it.  No  clearing  solution  is  necessary  as  this  de- 
veloper is  used.  For  soft  results  new  developer  is  recommended  ; 

5*i 


APPENDIX 


for  greater  contrasts  old  developer,  or  the  addition  of  a  few  drops 
of  a  10  per  cent,  potassium  bromide  solution. 

Toning.  By  following  the  above  instructions  the  finished 
prints  will  show  delicate  grey  or  rich  black  tones,  which  can,  if 
desired,  be  readily  changed  into  sepia  or  black  brown  tones  of 
equal  permanence  by  making  the  prints  somewhat  darker  and 
then  toning  the  finished  and  dried  picture  in  the  following 

Sepia  Toning  Bath. 

Sodium  hyposulphite...    io  ozs, 

Alum    ...    ...    I  oz. 

Boiling  water   70  ozs. 

Dissolve  the  hypo  in  the  water  first,  then  add  the  alum  slowly. 
When  all  is  dissolved,  the  solution  should  be  milk  white.  This 
solution  should  not  be  filtered,  and  it  works  better  when  it 
becomes  a  little  old ;  it  may  be  strengthened  from  time  to  time 
with  a  little  fresh  solution.  Never  throw  the  bath  away  entirely, 
but  replenish  in  the  manner  stated.  The  best  results  are  obtained 
by  keeping  the  bath  hot,  or  as  warm  as  the  emulsion  will  stand  ; 
say,  no°  to  1200  F.  In  this  bath  prints  will  tone  in  from  thirty 
to  forty  minutes.  A  new  bath  tends  to  reduce  the  prints  rather 
more  than  an  old  one.  When  toned,  the  prints  may  be  placed 
in  a  tepid  solution  of 

Water   70  ozs. 

Alum    2  „ 

Then  wash  thoroughly. 

Alum  bath.  When  a  toning  bath  is  to  be  employed,  the  use 
of  the  alum  bath  after  fixing  is  absolutely  essential.  Moreover, 
the  prints  should,  in  this  case,  not  be  subjected  to  a  prolonged 
washing,  but  should  only  be  slightly  rinsed  before  being  dried. 

Ilford  Bromide  Paper  and  Opals.  The  paper  is  made  in 
four  grades :  S.S  ,  smooth  slow ;  S.R.,  smooth  rapid  ;  R.S.,  rough 
slow;  R.R.,  rough  rapid.  The  slow  kind  is  suitable  for  both 
contact  printing  by  artificial  light  and  for  enlargement  for  day- 
light. The  rapid  for  enlargement  by  artificial  light.  The  question 
of  surface  is  one  of  taste  only,  though  the  rough  is  preferable  for 
large  work. 

5*2 


I.   plate-makers'  formulae. 


Exposure.  For  contact  work  on  slow  paper  place  paper  in 
printing  frame  under  negative  in  dark  room.  Expose  for  about 
twenty  seconds  at  twelve  inches  from  an  ordinary  fish-tail  gas 
burner  with  a  negative  of  average  density.  Rapid  bromide  is 
twenty  times  as  sensitive.  To  obtain  uniform  results  exposure 
must  be  made  under  uniform  conditions  as  to  light  and  distance. 

Development.  Make  the  following  solutions  and  use  when 
cold  : 

No.  i. 

Neutral  oxalate  of  potash 
Warm  water  ... 
Bromide  of  ammonium 

Filler. 
No-  2. 

Sulphate  of  iron        ...        ...    ...        I  lb.  av. 

Warm  water  ...       ...        ...        ...        ...       ...      48  o^s. 

Sulphuric  aeid ...       ...       ...       ...       ...       ...       1  drm. 

Kilter. 

For  use,  add  1  oz.  No.  2  to  6  oz.  No.  r,  not  vice  versa.  As  for 
Alpha,  old  developer  gives  brilliancy,  especially  in  cases  of  over 
exposure  or  weak  negatives.  Development  is  complete  when 
image  appears  fully  out.  After  development,  and  without  washing, 
immerse  the  prints  for  about  two  minutes  in  clearing  solution  ; 
pour  off,  and  repeat. 

Clearing  Solution. 

Water   So  ozs. 

Sulphuric  acid...       ...       ...       ...       ...       ...         .1  oz. 

Wash  thoroughly  for  about  ten  minutes  in  several  changes  of 
water.  All  the  acid  must  be  removed,  or  fading  of  prints  will 
result. 

Fixing  Solution. 

Water     ...     80  o/.s. 

Hyposulphite  of  soda  ...        ...        ...        ...        ...        1  II).  av. 

Allow  fifteen  minutes  for  thorough  fixation.  Use  fresh  solution 
for  each  batch  of  prints.    After  fixing  wash  for  two  hours  in 

513  L  L 


I  lb.  av. 

64  ozs. 
20  grs. 


APPENDIX. 


running  water,  or  in  frequent  changes.  Allow  prints  to  dry 
naturally.    Work  with  clean  hands  and  clean  dishes. 

Printing-out  Paper.  Working  instructions. — Printing.  This 
should  be  done  in  shade,  by  preference,  unless  negatives  are 
specially  strong  in  contrast.  The  image  loses  very  little  depth 
in  toning,  etc. 

First  washing.    For  fifteen  minutes  in  several  changes. 

Toning.  For  simplicity  and  excellence  of  results  we  recom" 
mend  the  following  : — 

Water     ...    16  ozs. 

Sulpho-cyanide  of  ammonium        ...    30  grs. 

Chloride  of  gold      2  f, 

The  prints  tone  in  this  bath  in  about  six  minutes,  and  it  should 
be  borne  in  mind  that  prints  dry  somewhat  darker  and  much 
colder  than  they  appear  when  wet.  The  bath  should  not  be  used 
many  times  ;  indeed,  it  is  well  to  make  a  stock  sulpho-cyanide 
solution  in  bulk,  and  take  as  much  of  it  as  is  needed,  adding  the 
gold  as  wanted.  A  bath  with  double  quantity  of  water  tends  to 
warm  tones. 

Second  washing.    For  five  minutes  in  several  changes. 

Fixing.  Use  new  solution  for  each  batch  of  prints.  The 
following  is  best  strength  : — Hypo,  3  ozs.  ;  water,  20  ozs.  Fixation 
is  complete  in  about  ten  minutes. 

Filial  washing.  For  at  least  two  hours  in  running  water,  or 
many  changes. 

Drying.  Lay  the  prints  face  upwards  on  the  blotting  paper 
(or  hang  up  by  clips)  and  allow  to  dry  naturally.  Mount  with 
starch  paste  in  usual  way. 

Alum  bath.  If  weather  is  hot,  and  the  surface  of  prints  becomes 
soft,  immerse  for  ten  minutes  in  alum  bath  (water,  20  ozs. ;  alum, 
2  oz.)  after  the  first  washing  and  before  toning ;  then  wash  for 
ten  minutes  before  putting  into  toning  bath. 

Special  notes.  Do  not  use  any  excess  of  sulpho-cyanide  over 
quantity  mentioned.  Use  the  washing  water  and  all  solutions 
as  cold  as  possible.  Keep  the  prints  moving  whilst  in  the  various 
solutions.    Above  remarks  apply  to  both  varieties  of  P.O.P. 

5T4 


t.   plate-makers'  formulae. 


Ilford  Alpha  Paper. 

Exposures.  Place  paper  in  printing  frame  under  negative  in 
dark  room.  Expose  at  six  inches  from  ordinary  fish-tail  burner 
for  two  and  a  half  to  three  minutes,  with  a  negative  of  average 
density.  To  obtain  uniform  results  exposures  must  be  made 
under  uniform  conditions  as  to  light  and  distance. 

Development  op  Alpha  Paper. 
Make  the  following  solutions,  and  do  not  use  until  cold : — 

No.  I. 

Oxalate  of  potash  (neutral)  ...        ...     I  lb.  avoir. 

Bromide  ammonium  ...        ...        ...    320  grains. 

Warm  water    . .        ...    64  oz. 

Filter. 

No.  2. 

Sulphate  of  iron      ...        ...        ...        ...    4^  ounces  avoir. 

Sulphuric  acid         ...        ...        ...        ...    1  drachm 

Water  ...      80  ounces. 

Filter. 

For  use  add  1  part  of  No.  2  to  3  parts  of  No.  1 ,  not  vice  versa. 
It  will  be  noticed  that  the  developer  is  weak  and  much  restrained, 
a  more  vigorous  formula  is  unsuitable.  The  prints  can  be  soaked 
in  water,  if  desired,  but  it  is  not  essential,  the  only  object  being 
to  secure  an  even  flow  of  developer  over  surface.  Development 
is  complete  when  image  appears  fully  out.  At  this  stage  a  . 
correctly  exposed  print  will  be  of  a  warm  brown  colour,  with 
a  peach  bloom  over  the  whole  surface.  Over-exposures  are 
indicated  by  a  yellowish  red  colour,  and  under-exposures  by  a 
greenish  black.  The  paper  gives  wide  latitude,  and  unless  the 
error  in  exposure  is  very  great,  perfect  prints  are  produced  by 
judicious  toning  (see  special  pamphlet,  free  on  application). 
Old  developer,  freshened  with  a  proportion  of  new,  just  before 
use,  gives  the  best  results.  This  is  best  kept  in  a  bottle  filled 
up  to  the  stopper,  replenished  from  time  to  time  as  required, 
with  the  two  solutions  freshly  mixed.  After  development,  and 
without  washing,  immerse  for  about  half-a-minute  in  clearing 
solution,  pour  off,  and  repeat. 

5"5 


Appendix. 


Clearing  Solution. 
Water,  80  oz.  Sulphuric  Acid,  ^  oz. 
This  has  a  reducing  action  on  Alpha  prints,  therefore  do  not 
allow  them  to  stay  in  the  bath  longer  than  time  given,  unless  it 
is  desired  to  correct  over-development.  Wash  thoroughly  for 
eight  to  ten  minutes,  in  several  changes  of  water ;  all  the  acid 
must  be  removed,  or  yellowness  of  whites  will  result.  Prints 
are  now  ready  for  toning  and  fixing,  which  can  be  done  by  gas  or 
subdued  daylight. 

Combined  Toning  and  Fixing  Bath. 

Water      10  ounces. 

Hyposulphite  of  soda   ...       ...       ...  2^  ounces  "j 

Acetate  of  soda  ...       ...       ...  jounce  J- Avoirdupois. 

Sulphocyanide  of  ammonium  ...       ...  £  ounce  J 

Chloride  of  gold  ...       ...       ...  4  grains. 

This  bath  should  be  made  forty. eight  hours  before  use  and 
allowed  to  clear ;  it  keeps  good  for  months  in  the  dark,  and  may 
be  used  over  and  over  again  if  replenished  from  time  to  time 
with  a  few  drams  of  a  stock  solution  made  up  as  above,  with 
5  of  water  only  and  double  quantity  of  gold.  The  constituents 
of  the  bath  must  be  added  and  dissolved  in  the  order  given. 

When  first  put  into  the  combined  bath,  the  prints  turn  yellow 
and  lose  all  their  vigour,  but  gradually  regain  both  colour  and 
strength,  and  toning  is  complete  in  about  a  quarter  of  an  hour. 
Prints  dry  darker  in  tone,  more  vigorous  in  image,  and  with 
more  detail  than  they  appear  when  wet.  After  toning  wash  for 
two  hours  in  running  water,  or  in  frequent  changes.  Allow  the 
prints  to  dry  naturally,  or  they  can  be  squeegeed  down  whilst 
wet  on  talced  glass,  matt  or  polished,  or  clean  ferrotype  plates, 
to  produce  matt,  or  enamelled  surface,  as  may  be  desired. 

Work  with  plenty  of  Yellow  Light.    Work  with  clean  hands  and 
dishes.    Keep  prints  constantly  moving  in  all  the  solutions. 

Ilford  P.O.P. 

Printing.  This  should  be  done  in  shade  by  preference,  unless 
negatives  are  specially  strong  in  contrast.  The  image  loses  very 
littl    depth  in  toning,  etc. 

First  washing.    For  fifteen  minutes  in  several  changes. 

516 


I.     PLATE-MAKERS  FORMULAS. 


Toning,  Any  of  the  recognised  formulae  for  this  class  of 
paper  may  be  used,  either  simple  toning  or  combined  toning 
and  fixing;  but  for  simplicity  and  excellence  of  results  we 
recommend  the  following: — Water,  16  oz. ;  sulphocyanide  of 
ammonium,  30  grains;  chloride  of  gold,  2  grains.  The  prints 
tone  in  this  bath  in  about  six  minutes,  and  should  be  withdrawn 
when  there  is  just  a  trace  of  warmth  in  the  heaviest  shadows  on 
looking  through  the  prints.  On  the  surface  they  will  appear 
overtoiled,  but  this  will  alter  in  the  fixing  bath.  This  toning 
bath  ca?i  be  used  at  once,  but  preferably  should  stand  for  twenty- 
four  hours  before  use.  When  it  becomes  dirty  or  refuses  to 
tone  properly,  a  new  one  should  be  made. 

Second  washing.    For  five  minutes  in  several  changes. 

Fixing.  Use  new  solution  for  each  batch  of  prints.  The 
following  is  best  strength  : — Hypo,  3  oz.  ;  water,  20  oz.  Fixation 
is  complete  in  about  ten  minutes. 

Final  washing.  For  at  least  two  hours  in  running  water,  or 
many  changes. 

Drying.  Lay  the  prints  face  upwards  on  the  blotting  paper 
(or  hang  up  by  clips),  and  allow  to  dry  naturally.  Mount  with 
starch  paste  in  usual  way.  Prints  thus  treated  and  passed 
through  roll  give  a  fine  glossy  surface,  better  than  albumen. 
This  paper  can  also  give  prints  of  enamelled  or  matt  surface  by 
squeegeeing  down  on  plain  or  ground  glass  in  the  usual  way. 

Alum  bath.  If  weather  is  hot,  and  the  surface  of  prints 
becomes  soft,  immerse  for  ten  minutes  in  alum  bath  (water, 
20  oz. ;  alum,  2  oz.),  after  the  first  washing  and  before  toning, 
then  wash  for  ten  minutes  before  putting  into  toning  bath. 

SPECIAL  NOTES. — Do  not  use  any  excess  of  sulphocyanide 
07/er  quantity  mentioned. 

Use  the  washing  water  and  all  solutions  as  cold  as  possible. 
Keep  the  prints  moving  whilst  in  the  various  solutions. 

Imperial  Bromide  Paper.  Smooth  or  rough  surface  for 
contact  printing  or  enlargements.  The  exposure  required  for 
Imperial  bromide  paper  will  be  found  to  be  the  same  as  for  slow 

517 


APPENDIX. 


opals,  and  according  to  the  developer  used.  The  developing 
formulae  I  and  J  are  recommended  for  rapidity  and  cleanliness 
in  working.  Negatives  with  strong  contrasts  should  be  printed  in 
a  strong  light,  weak  negatives  in  a  subdued  one.  The  treatment 
of  bromide  paper  in  development  is  very  similar  to  the  treat- 
ment of  bromide  opals.  In  drying,  however,  the  prints  should 
be  placed  face  upwards  on  clean  blotting  paper,  or  hung  up  with 
paper  clips. 

Imperial  "  Kloro "  Paper.  With  appropriate  treatment 
"  Kloro  "  paper  gives  superb  definition  ;  does  not  curl. 

Instructions.  Prints  must  be  only  slightly  darker  than  required 
when  toned  and  fixed.  Hard  and  fairly  dense  negatives  should 
be  printed  from  in  a  strong  light ;  weak  and  delicate  negatives  in 
the  shade  and  through  tissue  paper.  After  printing,  wash  for  ten 
minutes  in  running  water,  and  immerse  in  an  alum  bath. 

Alum    ...       ...       ...       ...       ...    \  oz. 

Water   ...       ...       ...       ...       ...      20  ozs. 

Leave  for  ten  minutes,  and  wash  again  in  running  water  for  five 
minutes. 

Toning.  Any  toning  formula  may  be  used,  but  the  finest 
results  are  obtained  with 

Sulpho-cyanide  of  ammonium    15  grs. 

Chloride  of  gold    I  gr. 

Water   8  ozs. 

This  bath  gives  beautiful  purple  tones.  Can  be  used  at  once, 
but  will  not  keep.  When  toned  sufficiently  place  in  a  bath 
composed  of 

Common  salt   1  oz. 

Water   20  ozs. 

to  prevent  further  toning.  Well  wash  the  prints  in  running  water 
and  fix  in 

Soda  hyposulphite 
Soda  sulphite  ... 
Water  

N.B. — Do  not  use  the  same  fixing  bath  twice. 

51S 


3  ozs. 

H  „ 

20  „ 


I.   plate-makers'  formulae. 


After  fixing,  wash  the  prints  for  one  hour  in  running  water. 
The  alum  bath  must  be  always  used  with  a  sulpho-cyanide  toning 
bath,  and  also  in  hot  weather  with  any  other  bath. 

Acetate  Bath  (Brown  Tones). 

'Soda  acetate    150  grs. 

Chloride  of  gold    5  „ 

Water   40  ozs. 

This  bath  keeps,  and  should  tone  equal  to  four  or  five  full  sheets 
of  paper  before  it  is  necessary  to  strengthen  it  by  the  addition  of 
more  chloride  of  gold.  The  bath  is  ready  for  use  twenty-four 
hours  after  being  prepared.  Special  care  must  be  taken  that  not 
the  slightest  trace  of  hypo  comes  into  contact  with  the  prints, 
toning  bath,  or  washing  solutions,  at  any  time  prior  to  fixing. 

Finishing.  If  a  glossy  surface  is  required,  dry  on  glass  pre- 
viously prepared  with  French  chalk.  If  a  matt  surface  is  required, 
dry  on  fine  ground  glass  previously  prepared  with  French  chalk. 
If  the  appearance  of  a  silver  print  is  desired,  dry  face  upwards 
on  blotting  paper  and  mount  with  starch  paste.  If  to  be  burnished 
the  alum  bath  musthz  used,  and  the  burnisher  is  not  to  be  heated 
to  more  than  1600.  Enamelled  prints  should  be  backed  with 
waterproof  paper  before  being  detached  from  the  glass  plate. 

Lumiere's  "  Citos "  P.O.P.  Citrate  of  Silver  Printing-out 
Paper  (mauve).  The  printing  of  the  positives  is  the  same  as 
with  albumenised  paper.  All  the  methods  of  toning  may  be 
made  use  of  with  these  papers,  but  the  following  formula?  are 
recommended  : — 

Combined  Toning  and  Fixing. 
A. 

Hot  water  ...       ...    17^  ozs.  or  1,000  parts. 

Hyposulphite  of  soda       ...        ...  7    ,,     ,,  400  ,, 

Citric  acid    ...       ...       ...       ...  15  grs.   ,,  2  ,, 

Ordinary  alum       ...        ...        ...  155     ,,     ,,  20  ,, 

Acetate  of  lead    15     „     „  2  ,, 

B. 

Water...       ...       ...       ...        ..       3.^  ozs.  or  100  parts. 

Chloride  of  gold        ...        ...        ...      15  grs.    ,,       I  part. 

Let  solution  A  remain  standing  for  several  hours,  then  filter 

5'9 


APPENDIX. 


carefully.  To  prepare  the  normal  bath  add  to  100  parts  of  A 
6  to  8  parts  of  B.  The  prints  may  be  immersed  directly  into 
this  solution,  but  by  previous  washing  more  vigorous  tones  may 
be  obtained,  and  the  bath  will  retain  its  qualities  for  longer.  In 
the  latter  case  a  small  quantity  of  alum  (i  to  2  per  cent.)  should 
be  added  to  the  first  water. 


Toning  and  Fixing  Separately. 
Toning. 

Hot  water,  1200  to  1400  F.         ...      17^  ozs.  or  1,000  parts. 

Precipitated  chalk ...        ...        ...      35  grs.    ,,        5  „ 

Chloride  of  gold  ( I  per  cent,  solution)    if  ozs.  „     100  „ 


This  solution  should  be  prepared  twenty-four  hours  beforehand  ; 
it  constitutes  a  "reserve  bath,"  which  will  keep  for  a  long  time. 
To  prepare  the  final  toning,  take  100  parts  of  water  and  15  parts 
of  this  solution.  The  prints  should  be  first  immersed  in  an  alum 
bath  (1  percent,  of  ordinary  alum),  then  washed  in  several  waters. 
It  is  necessary  to  use  both  the  alum  bath  and  the  ordinary  water 
bath  abundantly.  The  toning  is  then  done  as  in  the  case  of 
albumenised  paper  ;  the  prints  change  from  red  to  a  brown-purple 
after  twelve  to  fifteen  minutes.  This  tone  obtained,  they  are 
fixed  in 


Water   

Hyposulphite  of  soda 

Bisulphite  of  soda  

Ordinary  alum 

Nitrate  of  lead  (1  per  cent,  solution) 


17^  ozs.  or  1,000  parts. 

*t  „     „     150  „ 
45  grs-  v  6 
30    „     „        4  M 
115    m    „      15  »» 


Dissolve  these  ingredients  successively  in  the  order  named.  On 
being  put  into  the  fixing  bath  the  prints  become  a  yellowish-red, 
but  they  rapidly  change  to  reddish-brown  and  to  blue.  The  bath 
is  stopped  as  soon  as  the  desired  tone  is  obtained.  The  fixing 
bath  should  be  often  renewed.  The  diluted  toning  bath  can  be 
used  for  a  long  time  on  the  condition  that  it  is  strengthened  with 
the  "  reserve  solution,"  and  filtered  through  a  little  chalk  when 
the  toning  is  finished. 

520 


I.   plate-makers'  formula. 


Platinum  Toning. 

Water     ...       ...       ...        ...        ...  500  parts  or  16  ozs. 

Sodium  chloride  (salt)   2    ,,     ,,30  grs- 

Alum    5    „         75  „ 

Potassium  Chloro-Platinite    I  part   „  15 

Leave  the  prints  in  this  toning  bath  until  a  black  tone  is  obtained, 
then  wash  in  several  waters,  and  fix  them  in  the  combined  fixing 
and  toning  bath.  Images  treated  in  this  way  and  dried,  after 
washing,  on  ground  glass  have  the  aspect  of  the  most  beautiful 
platinum  paper,  and  a  delicacy  of  tone  which  the  latter  process 
cannot  give. 

General  observations.  Solutions  should  always  be  perfectly 
clear.  During  toning  the  prints  should  be  kept  constantly  on 
the  move.  Great  cleanliness  is  necessary  in  the  handling  of  this 
paper.  Yellow  stains,  which  might  appear  during  and  after 
toning,  are  only  stains  of  hyposulphite,  produced  by  contact 
with  the  fingers  or  with  uncleaned  dishes.  Care  should  be  taken 
to  remove  air-bubbles  in  case  they  form  on  the  surface  of  the 
paper ;  for,  even  after  the  first  washing,  the  little  red  stains 
which  might  appear  after  the  toning,  are  simply  due  to  these 
bubbles.  Sulphur  stains  are  never  produced  when  the  final 
washing  is  abundant  and  not  too  prolonged  ;  thus  it  is  advisable 
to  wash  the  prints  for  only  three  or  four  hours,  and  in  water 
changed  frequently.  Hang  up  till  completely  dry,  when  they 
can  be  cut  to  the  necessary  dimensions.  The  mounting  with 
starch  is  done  in  the  same  way  as  for  prints  on  albumenised 
paper.  They  can  be  burnished  hot  or  cold,  the  same  as  albu- 
menised paper.  In  any  case,  when  burnished  hot,  it  is  important 
that  the  prints  should  be  completely  dry. 

Brilliant  surface.  Prints  presenting  a  very  brilliant  surface 
may  be  obtained  by  transferring  on  to  perfectly  clean  glass, 
rubbed  with  a  solution  of  beeswax  in  benzine. 

Matt  effects.  Fine  matt  effects  may  be  obtained  by  transferring 
on  to  waxed  ground  glass,  with  the  customary  precautions  for 
these  transfers.  The  papers  should  be  protected  from  light  and 
from  dampness. 

5*« 


APPENDIX. 


Morgan  &  Kidd's  Argentic  G-elatino-Bromide  Paper. 

Developing  Solutions. 

No.  I.  Oxalate  Solution.  No.  2.  Iron  Solution. 

Potash,  neutral  oxalate...  l6ozs.       Iron  sulphate  (pure)  ...  15  ozs. 

Citric  acid    I  drm.      Citric  acid    I  drm. 

Hot  water   50  ozs.       Hot  water   30  ozs. 

No.  3.  Bromide  Solution. 

Bromide  of  potassium    ...        ...        I  oz. 

Water  ...    ...       ...    20  ozs. 

After  exposure,  soak  the  exposed  paper  in  the  water  while  mixing 
the  developer.  For  normal  developer  take  6  ozs.  No.  I,  add 
1  oz.  No.  2  and  6  drops  No.  3,  to  be  mixed  in  order  given  and 
immediately  before  using.  When  fully  developed,  rinse  the  print 
with  a  clearing  solution  of  1  oz.  of  acetic  acid  to  6  pints  of  water, 
immediately  the  developer  is  thrown  off  and  before  washing  with 
water.  The  clearing  solution  may  be  used  over  again  until  it 
becomes  discoloured.  After  well  washing,  immerse  for  about 
fifteen  minutes  in  the  fixing  solution : 

Hyposulphite  of  soda...       ...       ...       ...       ...       6  ozs. 

Water     40 

Wash  for  several  hours  in  changing  water,  clip  up  to  laths,  and 
hang  to  dry. 

Opal  and  canvas  enlargements.  The  same  formula  is  used 
for  enlargements  on  opal  or  canvas. 

Paget  Prize  Collodio -Chloride  Printing-out  Paper  (pink, 
white,  or  mauve).  Printing  should  be  somewhat  darker  than 
the  finished  print  is  required  ;  about  the  same  as  for  the  P.O.P., 
not  quite  so  dark  as  for  albumen. 

Was/ring.  Before  immersion  in  this  toning  bath  the  prints 
should  be  very  thoroughly  washed  for  at  least  five  minutes  in 
running  water,  or  in  three  or  four  changes.  If  the  dry  prints  are 
first  laid  face  downward  in  a  dish  of  hot  water,  as  warm  as  the 
hand  can  bear,  for  about  a  minute,  and  afterwards  in  two  changes 
of  cold  water,  the  washing  will  be  much  more  effective,  will 
overcome  any  tendency  to  curl,  and  the  toning  will  be  more 
satisfactory. 

522 


I.    plate-makers'  formutje. 


Salting.  After  washing,  it  is  advisable  to  place  the  prints  for 
about  one  minute  in  a  solution  of  common  salt,  strength  un- 
important, say  I  oz.  to  a  pint  of  water.  This  removes  any  last 
trace  of  silver  and  reddens  the  print,  so  that  the  progress  of 
toning  can  be  more  easily  judged.  After  salting,  wash  for  about 
five  minutes  before  toning. 

Toning.  Any  of  the  ordinary  toning  baths  employed  for 
albumen  or  gelatine  may  be  used,  but  no  bath  gives  such  rich 
brilliant  tones,  either  warm  or  cold,  as  the  sulphocyanide.  If  a 
little  care  be  taken  to  ensure  clean  dishes  and  clean  fingers,  there 
is  no  bath  more  simple  or  certain. 

Sulphocyanide  of  ammonia  ...        ...    30  grs. 

Gold  chloride   2  „ 

1  Water   ..       ...      16  ozs. 

Tone  to  exactly  the  colour  desired,  judging  the  prints  as  they  lie 
in  the  dish,  but  it  should  be  borne  in  mind  that  the  finished 
image  will  be  slightly  bluer  and  stronger  when  dry  than  in  the 
wet  state.    Wash  and  fix  in 

Hyposulphite  of  soda ...    3  ozs. 

Water   I  pint. 

Allow  at  least  ten  minutes  for  fixing.  Wash  thoroughly  in 
running  water  for  at  least  an  hour.  The  prints  may  then  be 
dried  between  blotting  paper,  or  quickly  in  a  moderate  heat. 
They  may  be  mounted  in  the  ordinary  way  with  starch,  and 
afterwards  rolled,  burnished,  or  enamelled,  in  fact  treated  in 
exactly  the  same  manner  as  albumenised  paper. 

Paget  Prize  Printing-out  Papers  (ordinary,  or  matt  surface). 
Printing  should  be  somewhat  darker  than  the  finished  print  is 
required.  It  should  be  borne  in  mind  when  toning  that  the 
finished  image  will  be  bluer  and  slightly  stronger  when  dry  than 
in  the  wet  state. 

Toning.  Either  of  the  following  well-known  baths  answers 
admirably  : 


Combined  Toning  and  Fixing  Bath. 
No.  1  Stock. 


Hyposulphite  of  soda... 
Alum  (potash  alum  only) 
Sodium  sulphate  (not  sulphite) 
Water  to   


20  ozs. 


5  u 
14  » 
I  gal. 


523 


APPENDIX. 


Dissolve  the  hypo  and  alum  each  in  about  one  quart  of  hot  water, 
mix,  and  then  add  sodium  sulphate  already  dissolved,  making  up 
to  one  gallon  with  remainder  of  water.  This  mixture  should 
then  be  left  for  some  hours  for  the  precipitate  to  settle,  when 
the  clear  solution  may  be  poured  off  or  filtered,  and  is  then  ready 
for  use.    It  will  keep  indefinitely. 


No.  2  Stock. 

Gold  chloride  ...        ..       ...       ...       ...  ...  15  grs. 

Acetate  of  lead                     ...       ...       ...  ...  64  „ 

Water  (distilled)   ...  8  ozs. 


Dissolve  the  acetate  of  lead  in  the  water  and  add  the  gold.  A 
heavy  precipitate  forms  in  this  solution,  which  should  be  shaken 
up  when  any  is  to  be  poured  out ;  it  redissolves  when  added  to 
No.  1  stock  solution.  For  use :  Mix  8  ozs.  of  No.  1  with  I  oz.  of 
No.  2.  When  this  bath  is  used  the  plates  should  not  be  washed 
before  toning. 

Separate  Toning  Bath. 

Sulphocyanide  of  ammonia  ...        ...        ...        ...      30  grs. 

Gold  chloride  ...       ...       ...       ...   i\  ,, 

Water  ...       ...       ...       ...       ...       ...       ...      16  ozs. 

Before  immersion  in  this  toning  bath  the  plates  should  be  very 
thoroughly  washed  for  at  least  fifteen  minutes  in  running  water. 
This  is  necessary  to  insure  even  toning.  In  hot  weather,  if 
necessary,  the  print  may  be  soaked  in  alum  (alum,  4  ozs.  ;  water, 
20  ozs.)  for  five  minutes  before  toning  in  this  bath.  Another 
thorough  washing  is  necessary  between  the  alum  and  toning 
baths. 

Fixing  Bath. 

Hyposulphite  of  soda...       ...       ...       ...       ...       3  ozs. 

Water   1  pint. 

After  fixing,  wash  well.  A  highly  glazed  surface  can  be  obtained 
by  squeegeeing  a  print  (on  the  ordinary  paper)  when  wet  on  to  a 
sheet  of  clean  glass,  previously  rubbed  over  with  French  chalk ; 
but  care  must  be  taken  that  the  French  chalk  is  well  rubbed  off. 
Burnishing  may  be  done  in  the  same  manner  as  with  albumen 
prints,  but  if  a  bar  burnisher  be  used  the  bar  should  not  be  much 
hotter  than  the  hand  can  bear  to  touch. 


t.   plate-makers'  formula. 


Rapid  Printing  on  Paget  Prize  Printing-out  Paper  by 
Partial  Development.  A  piece  of  this  paper  exposed  behind  a 
negative  in  the  ordinary  way  by  daylight  need  not  be  fully  printed, 
but  may  be  removed  from  the  frame  when  only  partially  printed, 
developed  up  to  the  necessary  strength  and  detail,  and  then  toned 
and  fixed  in  the  usual  manner,  with  exactly  the  same  results  as 
if  the  picture  had  been  fully  printed. 

Time  of  exposure.  A  very  slight  and  feeble  image  may  be 
developed  up  to  full  strength,  but  it  is  not  advisable  to  do  this, 
as  such  extreme  forcing  may  impair  the  purity  of  the  whites.  It 
is  recommended  that  not  less  than  one-tenth  of  the  full  printing 
time  be  given,  and  beyond  this  it  does  not  matter  how  much 
longer  the  printing  be  carried  on  ;  it  may  be  stopped  at  any  time 
short  of  full  printing.  Of  course  the  longer  the  printing  the  less 
the  development  required. 

Development.  Take  the  partially-printed  picture  from  the 
frame  and  immerse,  without  washing,  in  a  solution  of 

Potassium  bromide    ...       ...       I  oz. 

Water   ...    10  ozs. 

and  leave  it  for  at  least  two  minutes.  The  image  will  become 
yellow  in  colour  and  look  weaker  in  this  bath.  Now  wash  the 
print  in  running  water  for  at  least  three  minutes,  then  develop  it 
in  a  developer  composed  of  equal  parts  of  the  three  following 
stock  solutions  : 

Solution  i . 

Hydroquinonc 
Sulphurous  acid 
Sodium  sulphite 
Potassium  bromide 
Water  to 

Solution  2.  Solution  3. 

Caustic  soda   Jo/..        Bromide  of  ammonium  ...  10/.. 

Sodium  sulphite   V  „        Carbonate  of  ammonium     1  ,, 

Water  to   25  ozs.        Distilled  water  to  25  ozs 

Carbonate  of  ammonium  should  be  in  clear  lumps;  if  from 
exposure  to  the  air  it  has  become  coated  with  the  white  powdery 

525 


oz. 


f    1 1 

1 

•J  H 

60  grs. 
25  ozs. 


APPENDIX. 


bicarbonate  the  latter  should  be  scraped  off.  If  Solution  3  be 
made  with  ordinary  water,  it  will  be  cloudy  from  precipitation 
of  the  lime  in  the  water.  This  must  be  filtered  out,  or  left  to 
settle,  and  the  clear  solution  poured  off ;  otherwise  the  lime  may 
cause  spots.  Solutions  1  and  2  are  also  improved  by  filtering  or 
settling ;  as  undissolved  particles  of  any  kind  are  likely  to  cause 
spots.  More  of  No.  2,  up  to  double  the  quantity,  may  be  used 
with  the  effect  of  quickening  development ;  but  we  prefer  work- 
ing more  slowly.  The  time  of  development  will  vary  somewhat 
according  to  exposure  given,  etc.,  but  for  a  short  exposure  it  will 
average  from  three  to  five  minutes  Development  must  not  be 
carried  too  far,  as  the  image  gains  greatly  in  strength  in  the 
toning  ;  develop  until  nearly  all  the  picture  is  visible,  but  not 
the  very  fine  or  faint  details  ;  these  will  appear  afterwards  in 
the  toning.  When  sufficiently  developed  wash  at  once  and 
thoroughly  in  running  water  for  at  least  five  minutes.  If  the 
print  be  not  quickly  washed  so  as  to  get  rid  of  any  developer 
left  in  the  paper,  development  may  be  found  to  have  gone  on  too 
far  during  the  washing.  The  print  is  now  in  the  same  condition 
as  if  it  had  been  fully  printed  out  in  the  ordinary  way  and  washed 
(except  that  its  colour  is  different,  and  it  looks  much  too  weak), 
and  it  may  be  at  once  placed  in  either  the  sulphocyanide  or  the 
combined  toning  bath,  toned,  fixed,  and  treated  as  usual. 

Light.  All  the  above  described  operations  up  to  toning  may 
be  conducted  in  the  ordinary  light  of  a  printing-room  ;  that  is  to 
say,  in  daylight  which  has  passed  through  yellow  glass  or  a 
yellow  blind,  or  in  gaslight  or  lamplight. 


526 


II.  TABLES. 


THE  following  useful  tables  lor  calculating  the  time  of  exposure, 
according  to  A.  de  la  Baume  Pluvinel,  appeared  in  a  recent 
number  of  Nenheiten,  a  monthly  periodical  issued  by  Robert 
Talbot,  of  Berlin  : — For  the  time  of  exposure,  /,  of  a  photographic 
plate  applies  approximately  the  well-known  and  easily-proved 
formula — 

(  Focus  ) ■ 

t  =  constant  X  \  —  -  .  ,.    .  \ 

(  Diameter  of  diaphragm  ) 

in  which  the  constant  receives  certain  values,  first  empirically 
determined  by  Dorval.  In  this  formula  are  now,  however,  as 
one  perceives  at  first  sight,  several  important  factors  totally  dis- 
regarded, and  it  may  be  therefore  desirable,  on  the  ground  of  the 
laws  of  mathematical  optics,  and  with  the  aid  of  certain  necessary 
assumptions,  to  submit  the  problem  to  a  deeper  investigation, 
and  to  strive  to  bring  its  solution  into  better  harmony  with  the 
physical  facts. 

In  a  meritorious  brochure  (''  Lc  Temps  de  Pose,"  Paris,  1890, 
Gauthier  Villars),  issued  recently,  the  French  investigator,  De  la 
Baume  Pluvinel,  made  the  attempt  to  determine  a  formula 
applicable  to  any  possible  case,  according  to  which  "  the  time  of 
exposure  " — indeed,  any  time  can  be  reckoned  which  will  be 
required  to  expose  a  photographic  plate,  actually  an  ortho- 
chromatic — so  that  a  correct  printing  negative  will  be  finally 
obtained.  If  actually  La  Baume  Pluvinel's  theory  and  tables  of 
resultant  times  of  exposure  have  only  an  illusory  precision — 
which  is  to  be  expected  from  the  impossibility  of  aa  urate 

527 


APPENDIX. 


measurement  of  the  different  constants  which  arise — still  I  think 
that  it  will  be  welcome  to  the  reader  to  be  made  acquainted  with 
the  results  of  this  theory,  without  needing  to  follow  the  long 
mathematical  calculations  of  the  author,  and  therefore  I  briefly 
recapitulate  the  principal  results  and  empirical  data  of  La  Baume 
Pluvinel. 

However,  before  the  general  final  formula  for  the  time-exposure 
is  given,  the  units  of  the  factors  appearing  in  it  should  be  ex- 
plained, or  their  mathematical  expressions  be  given. 

An  important  factor  is  the  amount — 

log  Ajcos'a,  -  log  A2cos',rt2  4.0m 

A1cos',«1  -  A2cos4«2       X  pv  (1  —  e~mi) 

This  is  briefly  designated  In  which  e  represents  the  thick- 

ness of  the  gelatino-bromide  of  silver  film  ;  m,  its  absorptive 
coefficient ;  v,  the  absorptive  coefficient  of  the  film  saturated 
with  reduced  silver ;  ax  and  a>  the  angle  which  the  secondary 
axes  of  the  different  illuminated  elements  of  the  object  form  with 
the  principal  axis  of  the  objective  ;  A,  and  A2,  the  corresponding 
actinic  active  quality  of  light  (reckoned  for  units  of  time,  surface, 
and  distance).  One  can  now  actually,  for  any  single  case, 
approximately  reckon  the  value  of  -~ ,  with  the  help  of  certain 

assumptions,  and  on  the  basis  of  actinometrical  and  other 
measurements.  Still,  this  would  be  impracticable  for  practical 
work  ;  it  is  thus  better  to  estimate  ~  in  a  purely  experimental 

way  for  special  requirements,  and  the  different  cases  which 
occur  in  practice,  from  this  to  reduce  (see  the  table  of  the 
value  of  -g-  below).    This  also  applies  to  the  amount  J,  which 

represents  the  actinic  intensity  of  the  illuminating  beam  of  light, 
and  for  which  one  finds  a  table  below.  For  the  desired  time  of 
exposure,  /,  results  now,  according  to  La  Baume  Pluvinel's 
theory — 

■  i      JJ  J 

In  which  F  represents  the  equivalent  focus  of  the  objective  ; 

5^8 


II.  TABLES. 


I),  the  distance  of  the  object  from  the  lens,  measured  along 
the  principal  axis  ;  d,  the  working  aperture  of  the  lens — with 
doublets  d  =  p^ry  where  P  is  the  equivalent  focus  of  the  front 
lens,  d'  the  diameter  of  the  diaphragm,  /  the  distance  of  the 
centre  of  the  diaphragm  from  the  optical  centre  of  the  front  lens  ; 
N,  the  number  of  degrees  of  Warnerke's  sensitometer  which  the 
plate  used  shows.  N,  with  the  most  sensitive  plates,  =  25,  and 
varies  usually  between  16  and  23. 

The  co-efficient  r  ±*  with  landscape  is  about  1,  because 

t        D  I 

then  D  is  great ;  on  the  other  hand,  it  comes  considerably  into 
account  in  enlargements,  since  then  D  is  only  small.  In  the 
1  above,  it  must  be  noticed  that  the  absorption,  as  well  as  the 
reflection  of  the  lenses  of  the  objective,  is  not  calculated.  The 
same  has  a  mean  result  of  loss  of  light  of  about  20  per  cent. 


Value  of 


Clouds     ...       ...  ...   

. .  00005 

Sea 

..  OOOI 

Snow   

OOOI 

Ships  on  sea   

..  0  003 

Glaciers  with  rocks 

..  0  003 

Open  landscape  (panorama)  

..  0003 

Foliage,  with  water  or  white  houses... 

..  0005 

Foliage  only,  and  near  

..  o-oi 

Living  subjects,  portraits,  still  life,  etc. 

..  O'OI 

Reproduction  of  black  lines  on  white  ground 

002 

Value  of  _L  According  to  Eder,  Abney,  and 

VOGEL. 

Direct  upright  sunlight ;  for  Paris,  June  21st,  noon 

also  if  the  sun  stands  66°  above  the  horizon  .. 

I 

Diffused  light,  bright  weather   , 

4 

,,          „     sky  covered     , 

.    4  to  10 

Under  trees     

270 

In  the  studio   

12 

In  a  room,  1  metre  from  window   , 

7o 

Well-lighted  church                          ...   , 

200 

529 

M  M 

APPENDIX. 


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Morning. 

530 


II.  TABLES. 


ha 


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53 


APPENDIX. 


The  formula  determined  for  t  can  approximately  be  written 
as  follows : —  ,     T        i  F2 


For  this  the  values  of  L,  according  to  Dorval,  are  : — 


- 

Sunlight. 

Diffused 
Light. 

Cloudy 

Day. 

Morning'. 

Day. 

Morning 

and 
Evening. 

Panorama  and  sea  views  ... 

5  _ 
Totf  0 

TVS 

f  _ 
i  on 

tvv 

Panorama  with  large  masses 

of  foliage  ... 

1 

1  00 

2 

TVV 

TVV 

T^ 

0 

loo 

View  with  bright  foreground 

or  white  buildings 

T¥7> 

TVV 

Ttfo 

4 

ToTT 

View  with  dark  foreground 

or  dark  buildings... 

1  5 

\  o  oTf 

n 

1  -iV 

Tto 

e 

9 

1  1)  0 

Under    trees,  shady  river 

banks,  ravines,  etc. 

1  2 

TIT  IT 

2 

l? 

'3 

To 

Living  objects,  groups,  por- 

V 

traits,  etc.,  in  the  open  air 

4 

1  0  (7 

TITO" 

1  2 
10  0 

TJF 

The  same,  very  near  a  win- 

dow or  under  a  roof      .  . 

4 

1UTT 

8 

TVV 

TifV 

24 

Reproductions,  enlargements 

of  photographs,  engrav- 

ings, etc.  ... 

3 

10U 

r. 

nnr 

c 

TVV 

_2_5_ 

Day,"  in  Summer,  from  9  to  4;  in  Winter,  from  11  to  2. 


Holetschek's  Tables  calculated  for  Vienna  latitude. 


Chemical  Intensity  of  the  Light  from  a  Blue  Sky. 


Noon. 

na.m. 

10a.m. 

9  a.m. 

8  a.m. 

7  a.m. 

6  a  m. 

5  a.m. 

4  a.m. 

Jan.  21st  ... 

26-53 

25'53 

22*30 

16*42 

7'4i 

Eeb.  20th  ... 

32*22 

3i-43 

28-93 

24-14 

16-31 

5*i3 

March  20th  . 

36-23 

35'77 

34'io 

30-65 

24-64 

1532 

2*78 

April  21st ... 

38"07 

37'9o 

37-13 

35-12 

3o'99 

2414 

14*18 

'i':64 

May  22nd  ... 

38-30 

38-29 

38-02 

36-85 

33  98 

28-66 

20*62 

10*23 

June  21st  ... 

38-27 

38-30 

38-18 

37'27 

34*77 

30-06 

22*75 

13*14 

2  07 

July  21st  ... 

38-30 

38-29 

38  02 

36-85 

33  98 

28  66 

20*62 

10*23 

Aug.  21st  ... 

38-07 

37-90 

37-13 

35*12 

3o'99 

24*14 

14*18 

1*64 

Sept.  23rd... 

36-23 

35*77 

34*io 

30-65 

24-64 

15*32 

2*78 

Oct.  21st  ... 

32*22 

3i'43 

28-93 

24-14 

16-31 

5*i3 

Nov.  21st  ... 

26-53 

25*53 

22  30 

1642 

7-41 

Dec.  21st  ... 

22-63 

22*57 

19-14 

12  90 

3-48 

1 

Noon. 

1  p.m. 

2  pm. 

3  P-m. 

4  p.m. 

5  p.m. 

6  p.m. 

7  p.m. 

8  p.m. 

532 


I.  TABLES 


Chemical  Intensity  of  Direct  Sunlight. 


Noon. 

11  a.m. 

10a.m. 

9  a.m. 

8  a.m. 

-■ 

7  a.m. 

6  a.m. 

5  a.m. 



. 



10  97 

 _ 



o'8o 



29-81 

20'OQ 

827 

0*76 

ia'a" 

57  '64 

....  r 

9*18 

0  47 

9329 

88-17 

73*5* 

51-96 

27-87 

8-27 

0*25 

ni-77 

106-65 

9I-85 

69-52 

43-65 

19-24 

3'5o 

O'Ol 

1 17*44 

1 12*30 

97-77 

75 '62 

49-26 

24-11 

6-o6 

O'l  2 

111*77 

106*65 

91'85 

69-52 

43-65 

19-24 

3 '50 

O'OI 

93  "29 

88-17 

73-5I 

51-96 

27-87 

8-27 

0*25 

62-25 

57"64 

44-45 

26-44 

9-i8 

0-47 

33 '54 

29-81 

20-CK) 

8-27 

0*76 

F3'27 

10-97 

5*44 

o*8o 

7-40 

5-8i 

2'24 

0*10 

Noon. 

1  p.m. 

2  p.m. 

3  p.m. 

4  p.m. 

5  p.m. 

6  p.m. 

7  p.m. 

Jan.  2 1  st  . 
Feb.  joth  .. 
March  20th 
April  21st.. 
May  22nd  . 
June  22nd 
July  21st  .. 

AU£.  2ISt  ., 

Sept.  23rd 
Oct.  21st  .. 
Nov.  2ISt  ... 
Dec.  21st  .., 


Combined  Power  of  Blue  Sky  and  Sunlight. 


Noon. 

11  a.m. 

10a.n1 

9  a.m. 

8  a.m. 

7  ajn. 

6  a.m. 

5  a.m. 

4  a.m. 

Jan.  21st  ... 

39-80 

36*50 

27*74 

',-22 

7-41 

Keb.  20th  ... 

65-76 

61*24 

49*02 

32*41 

17*07 

5''3 

March  20th  . 

98-48 

93'4i 

78*55 

57-09 

33-82 

I5-79 

'2*78 

April  21st  ... 

i3'\36 

126*07 

110*64 

87-08 

56-86 

32*41 

14*43 

',"•64 

May  22nd  . . 

150*00 

144*94 

129*87 

106  37 

77-63 

47-90 

24*02 

19*23 

June  21st  ... 

I55-70 

150*66 

I35-94 

112*89 

84-03 

54-17 

28*21 

13-26 

2*07 

July  21st  ... 

150*07 

144*94 

129*87 

106*37 

77-6.3 

4790 

24*12 

10*23 

Aup.  21st  ... 

131-36 

126*07 

110*64 

87*08 

56*86 

32*41 

14*43 

i*64 

Sept.  23rd ... 

98*48 

93"4i 

78  55 

57-o9 

33-82 

15-79 

278 

Oct.  21st  ... 

65-76 

61*24 

49  *02 

3241 

17*07 

5-i3 

Nov.  21st  ... 

39-8o 

36*50 

27*74 

17*22 

7'4Ji 

Dec.  21  st  ... 

3i'03 

28*38 

21-38 

13*00 

3-48 

Noon. 

1  p.m. 

3  p.m. 

3  P-m. 

4  p.m. 

5  p.m. 

6  p.m. 

7  p.m. 

8  p.m. 

Miethe's  Table  of  Fixed  Foci. 

Distance  of  nearest  object 
in  focus  expressed  in  units 
Aperture.  of  the  focal  length. 

F/4  87 

...  70 


Example 


F/5  • 
F/6  . 

F/7  • 
F/io 
F/12 
F/15 
F/20 
F/30 
To 


working  at  F/lO. 


...  58 

...  50 

•••  35 

...  29 

...  23 

...  17*5 

...  ii*6 

find  the  nearest  point  in  locus  with  a  5-111.  lens 
5  x  35  =  175  ins.  =  14  ft.  7  ins. 


533 


APPENDIX. 


•«-o 


4-.  U5 


^50 


e»|» 


o    1  o 


;  2J.O 


1° 


S3  3 


o  O 

on 

.£  O 


8  8  „  § 


CO 


c  s  y 

■3  J  ft 

«J  £ 

a!  CO  6n 


h>3 

5  "2  Oh 


u 

O 


tin 


O 


O    !  o 


I? 

o 
0" 


u 
o 

o" 


534 


II.  TABLES. 


Piatt's  Tables. 

Table  I. — Subject  and  Light. 


„      ..           ..  ,  .    .      ,  - 

o in p i ic el  tinci  sii^xitly  3.itGrGQ  irom 
Eder's  and  Burton's  Tables. 

Sun 
shine. 

JL/  III  UoCU 

Light. 

Dull. 

v 

DulL 

Gloom. 

Sea  and  Sky   

j 

Panoramic  View   

2 

3 

4 

s 

Do.  with   Thick    Foliage,  or 

Strong  Foreground,  or  Light 

Buildings   

2 

4 

6 

8 

10 

Dark  Buildings   

3 

6 

9 

12 

15 

Heavy  Foliage  Foreground  ... 

4 

8 

12 

16 

20 

Woods   and    badly  lit  River 

Banks   ,.  ... 

IO 

20 

3° 

40 

50 

Living  Objects  Outdoors 

4 

8 

12 

20 

30 

Portrait  near  Window   

8 

16 

24 

40 

bo 

Interiors                  upwards  of 

IOO 

12 

20 

Copying  same  Size  

6 

Table  II.— Time  (Dr.  J.  A.  Scott). 


Hour  of  Day. 
a.m.  p.m. 

June. 

May. 
July. 

April. 
Aug. 

March. 
Sept. 

Feb. 
Oct. 

Jan. 

Nov. 

Dec. 

12 

2 

31 

4 

1 1 

1 

I* 

I| 

2. j 

4 

5 

IO 

2 

it 

IT 

3 

5 

6 

9 

3 

2 

4 

16 

8 

4 

2 

3 

10 

7 

5 

2 

3 

6 

6 

6 

2-J 

3 

6 

Yellow  Sunset 
affects  these  figui 

5 

7 

5 

6 

es. 

4 

S 

12 

535 


APPENDIX. 


Spitaler's  Table  of  the  Chemical  Intensity  of  the  Light 

for  every  ten  degrees  of  latitude,  for  the  northern  hemisphere, 
and  the  middle  of  each  month.  This  may  be  used  for  the 
southern  hemisphere  by  altering  the  time  of  year ;  thus,  January 
in  the  place  of  July,  etc. 


Latitude. 

o° 

IO° 

20° 

300 

400 

5o° 

6o° 

7o0 

8o° 

90° 

January   

408 

332 

2SO 



161 



80 

22 



1 



February   

437 

385 

315 

232 

146 

68 

March   

45i 

433 

391 

329 

251 

166 

84 

23 

April  

433 

451 

445 

414 

361 

288 

203 

113 

31 

May   

396 

442 

465 

464 

438 

388 

3i5 

212 

195 

203 

June  

373 

430 

467 

481 

469 

432 

367 

280 

3I3 

324 

July   

384 

432 

465 

47i 

452 

408 

34o 

222 

250 

259 

August   

418 

446 

45i 

43i 

388 

323 

242 

150 

69 

72 

September   

444 

438 

408 

356 

286 

204 

119 

45 

5 

October   

441 

399 

338 

261 

176 

94 

30 

2 

November   

415 

348 

266 

178 

96 

32 

2 

December  

397 

319 

231 

142 

64 

14 

Mean  of  the  Year  ... 

416 

405 

374 

327 

267 

203 

1 

146 

87 

! 

72 

74 

Tables  for  the  Simplification  of  Emulsion  Calculations. 

{Brit.  Joum.  Phot.  Almanac?) 

With  a  view  of  simplifying  the  calculations  involved  in  emulsion 
making,  Mr.  William  Ackland  has  worked  out  some  useful  tables, 
which  will  enable  even  those  most  ignorant  of  chemical  philo- 
sophy to  calculate  with  ease  and  rapidity  the  proper  quantities 
of  silver  or  haloid  salts  in  any  formula.  Even  those  who  are 
able  to  perform  the  calculations  in  the  recognised  style  will  find 
their  labours  materially  lightened  by  means  of  these  tables,  which 
should  be  kept  in  a  convenient  place  for  reference  in  every 
laboratory. 

536 


II.  TABLES. 


No.  I. 


Ammonium  bromide 
Potassium 
Sodium 
Cadmium 


com, 
anh 


Zinc  ,, 
Ammonium  chloride 
Sodium  ,, 
Ammonium  iodide 
Potassium 
Sodium  ,, 
Cadmium  ,, 


Weight 

Weight 

Weight 

Weight  I 

Weight 

of  silver 

of  soluble 

of  silver 

AgN03 

soluble 

haloid 

haloid 

haloid 

Equiva- 

required 

haloid 

pro- 

required 

pro- 

lent 

to  con- 

required 

duced 

to  pro- 

duced 

weights. 

vert  one 

to  con- 

by one 

duce  one 

from 

grain  of 

vert  one 

grain  of 

grain  of 

one 

soluble 

grain 

soluble 

silver 

grain 

haloid. 

AgN03. 

haloid. 

haloid. 

AgNOa. 

98 

1*734 

•576 

1-918 

•521 

\ 

119-1 

1-427 

■7OO 

1-578 

•633 

103 

1-650 

•606 

1-825 

•548 

-  1*106 

172 

•988 

I  OI2 

1-093 

•915 

136 

i-25 

•800 

1*382 

■723 

j 

j  1 2 '  1 

1  '509 

•663 

1*670 

*6oo  ; 

53'S 

3**77 

•315 

2-682 

•373  j 

}  -844 

58-5 

2-906 

•344 

2*453 

•408  j 

145 

1*172 

•»S3 

1*620 

•617  ! 

166-1 

1*023 

"977 

1*415 

■707  | 

1  - 

'150 

i*i33 

•882 

1-566 

•638  1 

183 

•929 

1*076 

1*284 

•778 

The  principal  bromides,  chlorides,  and  iodides  which  are  likely 
to  be  used  in  emulsions  of  either  gelatine  or  collodion  have  been 
included  in  these  tables.    Table  No.  1  presents  to  the  reader, 
without  any  mystification  which  may  be  involved  in  equivalents, 
the  actual  weights  of  haloid  or  silver,  as  the  case  may  be,  required 
to  convert  or  combine  with  one  grain  of  the  other.    In  order  to 
test  the  utility  of  this  table,  let  us  suppose  that  it  is  desired  to  make 
(say)  ioozs.  of  emulsion  by  a  new  formula,  which,  for  the  sake  of 
showing  the  working  of  the  table,  we  will  write  down  as  follow-  : 
Bromide  of  potassium  1 50  grains.      Chloride  of  ammonium  10  grains. 
Iodide  of  potassium       10     ,,  Gelatine      ...        ...    200  ,, 

Now,  we  want  to  know  how  much  silver  nitrate  should  be  em- 
ployed in  sensitising  this  mixture.  For  this  purpose  we  use  the 
first  column,  in  which  we  find  against  each  haloid  the  exact 
quantity  of  silver  nitrate  required  to  fully  decompose  one  grain. 
Taking,  then,  the  figures  we  find  in  column  No.  1  against  the 
three  salts  in  the  above  formula,  and  multiplying  them  by  the 
number  of  grains  of  each  used,  we  have  the  following  sum  : — 

Potassium  bromide       150x1427  =  214     j  Weight 
„         iodide  10  X  1*023  =    10*23  >  silver  nitrate 

Chloride  of  ammonium    10x3-177=    31*77  /  required; 
or  the  total  quantity  of  silver  nitrate  required  for  full  conversion, 
256  grains. 

537 


APPENDIX. 


•apipoi 
umimpe3 


•apipoj 
mnipog 


•apipoi 
utnissBjoj 


•apxpoj 
uintuouiiuv 


uimpoc, 


ro      •>*■  *0 


ct)      ro  on 


2   *  g 


5-  ? 


M  M  M 


uiniuotumv 


•aptuicug 

3UJZ 


(•p.Cijuv) 
•apiuicug 
uiniuipB3 


(•11103) 
•apiuicug 
uiniutpB^ 


'apimcug 
umipog 


•apiuiojg 


•aptmcug 
uiruiiouiuiy 


VO  1- 


N  < 


538 


1-  e  ci.5  «-  u;H 

S  §    e  2  s 

If  8*6?*  2 
ujx  «  o).S 

i>£  §>S  6~  2 

-Q  jh  <G  oj  g  be 

-z  a  <u  g  ■"->  t  w 

°  .2  £  a  5  c 

S  8  °  «  «  S  ~ 


<S  £~<~  6  in  M 


§  w^.s  g 

u  <u  rt^tG  a,  >- 
<u  c-a  <u  a)  >  2 
>  o  <u  m  >-~  c 

3  D  E  3.     «  t) 

«  y  «  <u "  ~U  .G 
g  2  0  -G  3  +» 

"SI  ^  ?  o 

.5*5!  .£"8  .^1 

<U  "  o,1*-1  m  rt  m 
.£  O  «>  °  .22       W  D 

a  site  o 

£  W>StJ  §  bC~G 


(U^S  cn ' 


II.  TABLES. 

Soret's  Tables  of  Angles  included  by  a  Lens. 


Diagonal  of  the 

Angle  included 

Diagonal  of  the 

Angle  included 

plate. 

by  lens. 

plate. 

by  lens. 

2/  +  if 

1 00  It) 

J  +  u 

50  0 

2/  +  \J 

io2  43 

J  +tV/ 

en0  n' 

57  37 

2/  +  sf 

9»  50 

-f 

J 

53  0 

n  r  .     1  f 
2/  +  4/ 

r»ft°   yl  /I  ' 

f      1  f 
J  —  TV/ 

/1«0  -7*7' 

45  27 

2/ 

90 

1  f 

47  54 

/  +  t/ 

82°  22' 

f       »  f 
f  —  h/ 

47  *5 

/  +  #7 

1            J    —  if 

46°  24' 

72"1  44' 

f  _  ' 

40     I  1 

/  +  |/ 

670  31' 

/-  1/ 

44°  23' 

/  +  1/ 

640 

/-  if 

410  7' 

/  +  \f 

•6i°55' 

/"  hf 

36°  52' 

f  +  If 

6o°  30' 

f~  hf 

280  4' 

f+tf 

59°  28' 

if 

180  36' 

f  +  if 

580  42' 

1/ 

1 40  20' 

Example :  What  angle  is  included  by  a  12-in.  lens  on  a  plate  the 
diagonal  of  which  is  10  ins.  12  —  10  or/  +  and  against  this  we 
find  6i°  55'. 

Table  of  Indices  of  Refraction  (for  D). 


Phosphorus 

Carbon  disulpl 

Oil  of  cassia 

Aniline  ... 

Nitrobenzine 

Phenol 

Cubebine... 

Pseudocumene 

Benzine  ... 

Glycerine 

Turpentine 

Chloroform 

Amylic  alcohol 

Ethylic  alcohol 

Ether 

Acetone  ... 
Methylic  alcohol 
Water  ... 


1  -075 

I*634 
1-580 
1-570 
1-540 
I-550 
I-5IO 
1490 
1490 
I-470 
1-460 
1-440 
1-400 
1-390 
I-350 
1-350 
I'TI 


539 


APPENDIX. 


Equations  Relating  to  Foci,  etc. 

{Brit.  Journ.  Phot.  Almanac.} 

The  following  simple  optical  formulae  and  calculations,  worked 
out  by  Mr.  J.  A.  C.  Branfill,  will  prove  useful  in  many  branches 
of  photography,  especially  where  several  lenses  of  varying  foci 
are  in  constant  use  for  a  variety  of  purposes  : — 
Let      p  =  Principal  focus. 

F  =  Greater  conjugate  do. 
/  =  Lesser       do.  do. 
D  —  F  +  /=  distance  of  image  from  object. 
y  =  Ratio  of  any  dimension  in  original  to  the  same  dimension 
in  copy  (in  case  of  reduction),  or  vice  versa  (in  case  of 
enlargement). 
a  =  Effective  diameter  of  diaphragm. 
U.  S.  No.  =  "  Uniform  System  "  No.  of  do. 

x  =  Comparative  exposure  required. 

Ff        F  yf 


Then         p  —  D 


(y  +  i)-      D      y  +  1      y  t  i 


f  = 


7) 


U.  S.  No. 


r~ 

N.B.— For  ordinary  landscape  work,  where  r  is  greater  than  20,  x 
may  be  taken  as  — 

IOrt" 

Note.— In  case  the  above  may  not  be  clear  to  some  photographers, 
the  following  rules  may  be  better  understood  : — 

To  find  the  principal  focus  of  a  lens  (/>),  focus  a  near  object  in  the 
camera,  and  measure  the  distance  between  it  and  the  ground-glass 
(D);  next  find  the  proportion  which  any  dimension  in  the  object 
bears  to  the  same  dimension  on  the  ground-glass  (/-).  Thus,  if 
the  original  dimension  be  four  times  as  large  as  its  reproduction,  we 

540 


II.  TABLES. 


say  that  r  equals  (  =  )  4.  Multiply  D  by  r,  and  divide  the  product 
by  the  square  of  a  number  greater  by  one  than  r  (r  +  i)\  This  rule 
was  lately  published  by  Mr.  Debcnham. 

To  find  the  lesser  conjugate  focus  (/)  (if  p  and  r  are  known) 
multiply  p  by  the  sum  of  r  +  1  and  divide  the  product  by  r.  Or 
divide  D  by  r  +  I, 

To  find  the  greater  conjugate  focus  (F)  multiply  p  by  r  +  1.  Or 
multiply  /  by  r. 

To  find  D  (the  distance  which  the  ground-glass  should  be  from  the 
object  to  be  copied  in  order  to  get  a  given  value  for  r)  multiply  p  by 
1 


*:he  sum  of  r  +  -  +  2. 

r 


Or 


To  find  r  divide  F  —  p  (the  difference  between  F  and  p)  by  p. 
divide  p  by/  —  p.    Or  divide  F  by  /. 

To  find  .r  divide  the  square  of /  by  16  times  the  square  of  a  (the 
diameter  of  aperture  to  lens). 

For  example  :  focus  an  object  which  is  five  inches  high,  so  that  it  is 
one  inch  high  on  the  ground-glass;  thus  we  know  that  r  =  5.  Next 
measure  the  distance  between  the  object  and  the  ground-glass  (Z)). 
which  is  found  to  be  45  inches. 

Then  p  =  45  x  (multiplied  by)  5  -f-  (divided  by)  6x6  =  6^  inches, 
f=6\  x  6  -f-  5  =  J\  inches.    Or /=  45  -f-  6  =  "j\  inches. 
F  —  6}  x  6  =  37^  inches.    Or  F=  7 J  x  5  =  37^  inches. 
D  =  6\  x  (5  +  I  +  2)  =  6\  x  7i  =  45  inches. 
r  =  (37i-6*)-S-6*  =  5.   Or  r  =  6*  +  (7*  -  6*)  =  5. 

Cadett's  Table,  showing  the  relative  Rapidities  of  Plates  of 
varying  Sensitometer  Numbers. 

Number  of  times  more  sensitive  than — 


25     24  23 


[9      18      17  16 


I  \\\\ 

li  1 

?! 

3 

4 

5 

7 

9 

12 

—  I 

2j 

3 

4 

5 

7 

9 

i* 

ii 

*i 

3 

4 

5 

7 

i| 

2} 

3 

4 

5 

1 

M 

ii 

2i 

4 

1 

ii 

2| 

3 

1 

Ii 
I 

I| 
ij 

2  J 

I 

1 

25 
24 
2  3 
22 

21 

20 

19 
18 

17 

16 

15 

A 

To  use  this  table  to  compare  the  rapidity  of  two  plates,  the 
sensitometer  numbers  of  which  are  known,  run  the  eye  up  the 

541 


15 
16 
12 
9 
7 
5 
4 
3 

2\ 

ii 

1 1 
1 


APPENDIX. 


column  A  till  the  sensitometer  number  is  reached,  and  then  along 
the  line  of  figures  till  it  reaches  the  column  of  figures  under  the 
sensitometer  number  of  the  second  plate,  when  the  figure  there 
shown  will  tell  at  once  the  difference  in  rapidity.  Example — A 
plate  has  been  used  of  ordinary  rapidity  showing  18  on  sensito- 
meter, and  it  is  desired  to  use  a  plate  of  sensitometer  No.  22  : 
what  will  be  the  reduction  in  exposure  ?  Find  22  in  column  A, 
and  carry  the  eye  along  the  line  of  figures  opposite  to  it  till  it 
meets  the  column  under  18  in  B  line — the  number  3  will  be 
found  ;  therefore  the  22  plate  is  three  times  as  sensitive  as  the 
No.  18,  and  will  therefore  require  one-third  of  the  exposure. 


Table  of  Exposures  for  Enlarging. 

By  E.  Ferrero. 


ot&nley  s 
Actinometer. 

/A6 

f/2? 

//32 

//48 

//72 

//too 

Seconds. 

min.sec. 

min.sec. 

min.sec. 

min.sec. 

min.sec 

min.sec. 

min.sec. 

min.sec. 

IO 

0  9 

O  17 

O  23 

O  36 

0  55 

I  20 

3  0 

5  47 

15 

O  13 

0  25 

0  34 

0  54 

1  23 

2  O 

4  3° 

8  40 

20 

O  18 

O  32 

O  46 

I  12 

1  5i 

2  40 

6  0 

"  34 

25 

O  22 

O  42 

0  57 

I  30 

2  18 

3  20 

7  30 

14  27 

30 

O  27 

O  49 

1  9 

I  48 

2  46 

4  0 

9  0 

17  21 

40 

O  36 

■  5 

1  34 

2  24 

3  42 

5  20 

12  0 

23  8 

50 

0  45 

1  24 

1  54 

3  0 

4  36 

6  40 

15  0 

28  54 

60 

0  54 

1  38 

2  18 

3  36 

5  32 

8  0 

18  0 

34  42 

70 

1  3 

1  54 

2  42 

4  12 

6  28 

9  20 

21  0 

40  29 

80 

1  12 

2  10 

3  7 

4  48 

7  24 

10  40 

24  0 

46  15 

90 

1  21 

2  29 

3  28 

5  24 

8  18 

12  0 

27  0 

52  0 

IOO 

1  30 

2  48 

3  48 

6  0 

9  12 

13  20 

30  0 

57  48 

I20 

1  48 

3  16 

4  36 

7  12 

n  5 

16  0 

36  0 

69  24 

I40 

2  6 

3  48 

5  23 

8  24 

12  56 

18  40 

42  0 

81  0 

l6o 

2  24 

4  20 

6  14 

9  36 

14  48 

21  20 

48  0 

92  0 

180 

2  42 

4  58 

6  56 

10  48 

16  36 

24  0 

54  0 

104  0 

200 

3  0 

5  36 

7  36 

12  0 

18  25 

26  40 

60  0 

1 16  0 

225 

3  22 

6  18 

8  33 

13  30 

20  45 

30  0 

67  30 

130  0 

250 

3  45 

7  0 

9  30 

15  0 

23  0 

33  20 

75  0 

144  0 

275 

4  7 

7  42 

10  27 

16  30 

25  20 

36  40 

82  30 

159  0 

300 

4  30 

8  24 

11  24 

18  0 

27  40 

40  0 

90  0 

174  0 

The  table  shows  the  exposures  to  be  given  to  Eastman's  and 
Britannia  slow  bromide  papers,  according  to  the  actual  intensity  ratio 
of  the  lens,  and  to  the  actinic  power  of  light  as  measured  by  Stanley's 
actinometer.  Britannia  rapid  bromide  paper  requires  one-fiftieth  of 
the  exposure  indicated,  and  gelatino-bromide  plates  of  ordinary 
rapidity  one-fifteenth  to  one-twentieth. 

542 


II.  TABLES. 


Holetschek's  Table  of  Drop-shutter  Speeds. 


Distance  of 
the  opening 
of  the  drop 

shutter 
above  the 
aperture  of 
lens. 

2  cm. 

4  cm. 

6  cm. 

8  cm. 

iocm. 

15  cm. 

20  cm. 

25  cm. 

30  cm. 

o    U  cm. 

<jj  c  (  o  cm. 
rt™  J7  cm. 
5    \8  cm. 

1 

TTT 

tV 

a 
} 

t 
l 

iV 

A 

rr 

sV 
i 

1 

tV 

t 

1T5 
1 

"2-5" 
l 
3  f 

■55 
1 

tV 

* 
1 

5T 
1 

5T 

1 

J 
?TS 
1 

IT  3" 

1 

TS7 

n 

TiV 

1 

1 

1  c 

\  u 

I  VI  O 

I  O  w 

1   Q.  <U 

X  <" 

To  use  this  Table  find  the  distance  of  the  opening  of  the  dropping 
piece  of  the  shutter  above  the  lens,  measuring  from  centre  to  centre 
of  each.  Example: — Assume  this  to  be  8  cm.,  the  lens  has  a  diameter 
of  20  cm.,  the  time  of  exposure  is  £g  sec. 


Table  of  equivalents  of  Haloid  salts  which  are  required  to 
decompose  170  parts  of  Silver  Nitrate.  (Eder.) 


Sodium  chloride  ... 
Potassium  chloride 
Ammonium  chloride 
Calcium  chloride  ... 
Crystal  calcium  chloride  ... 
Strontium  chloride 
Anhydrous  strontium  chloride 

Lithium  chloride  

Magnesium  chloride 
Anhydrous  magnesium  chloride 
Zinc  chloride 
Cobalt  chloride 
85-25  Crystal  cupric  chloride  ... 
119*1    Potassium  bromide 
Sodium  bromide  ... 
Anhydrous  sodium  bromide 
Strontium  bromide 
Ammonium  bromide 
Zinc  bromide 
Cadmium  bromide 
Anhydrous  cadmium 
126-33  Cadmium  and  ammonium  bromide  (2NH4Br,2CdBrHtO) 

166-1    Potassium  iodide  (KI). 

186-0   Sodium  iodide   (Nal2H,0). 

543 


58-5 
74-6 

53'5 
55-5 
109-5 

133-2 
79-2 

42-5 
101-5 

47-5 
68-o 
1 19.0 


1390 
103-0 
1774 
980 
1 125 
1720 
1360 


(NaCl). 
(KC1). 
(NH.Cl). 
(CaCl3). 
(CaCL6H„0). 
(SrCl,6H.;0). 
(SrCL). 
(LiCl). 

(MgC!.,6H„0). 
(MgCL).  " 
...  (ZnCl2). 
...  (CoCl,6H,0). 
...  (CuCUH'2Cv 
...  (KBr). 
...  (NaBr2H.,0). 
...  (NaBr). 
...  (SrBr26HX>). 
...  (NH4Br). 
...  (ZnBr2). 
...  (CdBr»4H,0). 
(CdBrJ.  " 


APPENDIX. 


187-54  Lithium  iodide   (Lil3H20). 

145-0   Ammonium  iodide   f  NH.jI). 

159-5   Zinc  iodide   (Znl2). 

182*5   Cadmium  iodide    ...        ...        ...  (CdL,). 


Table  of  Specific  Gravities  of  Chlorides. 


Salt, 
per  cent. 

1  ■So- 
PQ 

U  J? 

n° 
US 

U 

-V 

U   m  M 

@  7*1 

(/)  4-  ca 

—  0  - 

U  £ 
u 

2 

I -0144 

1-0183 

i  "0 1 70 

1-0198 

I*Ol82 

1  *o  1 46 

— 

I  "0I05 

IOI3 



I  OlO  I 

A 
4 

1-0288 

1-0367 

I  •02.06 

I -026/1 
1  UJU4 

1  0292 

1  u33° 

I  "026 

t  •n2<:i'> 

6 

I -0435 

IO557 

T  *OCnC 

I  "0548 

I,0439 

I  "040 

1  *-04° 

8 

1-0584 

I -0754 

I-0682 

I  O795 

I'°734 

1-0587 

1  UO04 

I'°54 

1-0738 

10 

I 0734 

I-095I 

I  -0869 

1  U997 

1-0734 

1-0859 

ro68 

1 2 

1-0890-  1-1164 

i-io-"6 

I'I228 

i-i  178 

1  -0894 

I  ■ 1 04C 

1*082 

T  •  I  I  22 

T/l 

1-1047  I-1378 

1 -12/12 

I '  1 460 

I*  1/126 

I  •  TOC  A 

I ' 1 22C 

I  "007 

1 "  I  227 

16 

1-1207!  ri6oo 

T*I/122 

I '  1 71 1 

I -1696 

1*1215 

I ' 1 404 

1*112 

1  x^49 

18 

1-1820 

I-l628 

T  •  T  275^ 

T  •  t  cni 

1  o9J 

1*128 

I  •  T  76n 

20 

I'l  £27 

I  "206 1 

I '  l822 

1  ^^45 

ri542 

1 '  1 780 

T  '  T  /I  A 
144 

I '  1 989 

22 

I  '  T  700 

T  "7  2  T  7 

I -2028 

T2.X.A  7 

I  -2501 

T*  T  1  a(\ 
1  I74O 

T  •  T  r>7& 
1  1970 

i'i6i 

I  -2225 

2/1 
^4 

1-1881 

1-2574 

T  '22  2/1 

1  -2849 

T  *277n 

1  2/79 

I-I950 

t  "7  i  7  e 

T  *  T  77 
1  1/7 

I  -2462 

26 

1  '2058 

1*244  **. 

i-3o-*8 

1  JUJ° 

I  *2 1 1*.  C 

T  -2278 

I  '104 

1-2708 

28 

1-2241 

1*2662 

I  "2228 

I  -  226  C 

I-2586 

1*212 

1*2964 

0° 

1-2422 

1*2879 

1*2618 

1-2568 

I  "220 

t  -2220 

oz 

1-2615 

I  •  2  TO/I 

t  *2r>Cr> 

1  277O 

T  ">  AtS 

1  o495 

•2  A 

34 

1-2808 

t  •  1 2  2r» 

1  333° 

1  4^07 

T  "?r>88 

1  zyoo 

1*268 

^6 

1-3007 

1  35DI 

1  -46 1 5 

I'3I99 

1*288 

18 

1-321 1 

!'3797 

1  4949 

1-341 1 

1*309 

4U 

i'34i5 

I,4°33 

I  5204 

1-3622 

1'330 

42 

I  3070 

T">ro 

1  3^-i 

44 

"! 

I  -41  18 

T  '27/1 
1  J/4 

46 

T  'A  -iftl 

1  43°7 

I  *207 

1  .597 

48 

1-46 1 7 

1  •  AO  1 

1  4^1 

50 

1-4867 

1-445 

52 

1  3*3j 

T  '/I  7  T 

1  4/  1 

54 

;•• 

1-5439 

i*497 

56 

1-5729 

1-525 

58 

1-6023 

1-554 

60 

::: 

1-6317 

1-582 

62 

1*613 

64 

1-644 

66 

1-677 

68 

1*711 

70 

::: 

1-745 

72 

... 

1-783 

74 

1 '82 1 

544 


II.  TABLES. 


Salt, 
per  cent.  | 

Ammonium 
Chloride. 

Potassium 
Chloride. 

Sodium 
Chloride. 

Potassium 
Carbonate. 

Potassium 
Bichromate. 

Salt, 

per  cent. 

Potassium 
Carbonate. 

1 

I  -00j2 

I  0065 

I  007  7 

I  C09 1 

1-007 

27 

1-20/9 

2 

I  'OO63 

f  -n  1  in 

I  "O  I  A  C 

|  1  UI4j 

1015 

28 

I  -2789 

o 

I  OOQ  ? 

I'OIQC 

I  '02  I  7 

I  "027A 

1  "022 

I  -2900 

A 
1 

I  'OI26 

I -0260 

I  "02C  O 
I  'O  l()7 

I  '0366 

I  029 

^0 

I  "2 "MO 

C 

rOI58 

I  '012  C 

I  'OA  Z  7 

I  '0  7  7 

1 1 

I'l  I  26 

6 

roi88 

I  '0302 

I  "OA  ifi 

I  -oss  I 

I  'OA  7 

32 
J 

7 

1  '02 18 

I  O458 

I  '05  I  I 

I  'O645 

I  'O5O 

33 

i  • 1  3  cS 
1  j3j° 

1  -0248 

TOC2C 

1  'O74O 

I  "056 

•2/1 

1  j47j 
i-3s88 

Q 

1*0278 

1  O^O  I 

I  0659 

I  C834 

I  065 

;c 
JJ 

IO 

1 -0^08 

IO658 

I  '07  2  1 

I  O928 

I  07^ 

^6 

1  •  1 70S 

I  I 

I  '08  IO 

I  I026 

I  '080 

37 

1  •  1828 

I  2 

T  T>  ?66 

I  "0796 

1  -0886 

I'll  24 

I  'O9O 

?8 

I  7 

I  'O  sQ<\ 

I  -0865 

1  '0962 

I "  I  222 

I  007 

jy 

I  4067 

1  A 

1  'OA  X2 

I  "OQ^d. 

1  ■  1028 

r  1320 

1  "  IO  J 

AO 

f  c 

I  "0452 

1  - 1004 

ri  1 15 

[-I418 

I '  I  10 

4  I 

16 

I  O480 

1-1075 

1-1194 

I  I52O 

42 

1-4434 

17 

IO509 

1  •  1 1 46 

11270 

ri622 

43 

i'4557 

18 

I-0537 

I-I2I8 

I-I352 

I-I724 

44 

1-4681 

19 

I-0565 

1-1289 

1-143' 

1-I826 

45 

1  -4804 

20 

I -0593 

1-1361 

1-1511  | 

I  1929 

46 

14931 

21  ; 

I  062O 

11435 

II593 

1-2034 

47 

1-5059 

22 

I-0648 

1-1509 

11675 

12  140 

48 

1-5180 

23 

I-0675 

1-1583 

1-1758 

1-2246 

49 

i-53i3 

24 

I-0703 

1-1657 

1  •  1 840 

12352 

5o 

15441 

25 

PO73O 

1-1923 

1-2457 

5i 

1-5573 

26 

I -Q737 

12010 

1-2568 

52 

15705 

Table  of  Specific  Gravities  of  Solutions  of  Phosphoric  Acid 
at  15°  C. 


Specific 
Gravity. 

P04H?. 
Per  Cent. 

F2O.V 
Per  Cent. 

Specific 
Gravity. 

P04H3. 

Per  Cent. 

P.O.. 
Per  Cent. 

1-476 

6404 

47lO 

I  236 

3769 

27  30 

1-442 

60-90 

4413 

1*197 

32-IO 

23-23 

1-418 

58-22 

42-61 

1  162 

27-24 

1973 

I-384 

55-40 

40- 1 2 

1-136 

23-41 

1695 

1-356 

52-46 

38-00 

1109 

1830 

13-25 

1-328 

5093 

36- 1 5 

1  066 

I  I  9 1 

862 

1293 

45-05 

3271 

1-031 

5-73 

415 

1-268 

4160 

•  30-13 

roo5 

I- IO 

079 

545 


APPENDIX. 


Table  of  Specific  Gravities  and  Strengths  of  Chromic  Acid. 


Specific  Gravity 
at  i7°i. 

Per  cent. 
Cr03. 

Specific  Gravity 
at  i7°5- 

Per  cent. 
Cr03 

1-037 

5 

1-258  • 

30 

1076 

10 

1-373 

40 

i'n8 

x5 

1-512 

50 

1162 

20 

1-665 

60 

1  208 

25 

Table  of  Specific  Gravities  of  various  Salts. 


Salt,  per  cent. 

il 
11 

(f)  a 
X 

Barium 
Nitrate. 

Strontium  j 
Nitrate. 

1 

Magnesium 
Nitrate. 

Lead 
Nitrate. 

Potassium 
Oxalate. 

Potassium 
Chromate. 

Platinic 
Chloride. 

Potassium 
Ferrocyanide. 

2 

1-0105 

I  OI 7 

I-OI7 

1-0078 

1-0163 

1-0134 

*  1 

1-0161 

IOI8 

I. OI  16 

4 

I  02 1  I 

1-034 

I  034 

1-0158 

1-0331 

I -0268 

1-0325 

1-036 

1-0234 

6 

1-0317 

I  05O 

I  049 

1-0239 

1-0502 

1-0401 

10492 

1-056 

1-0356 

8 

1-0423 

1*069 

ro68 

IO32 1 

I  0682 

1-0529 

1-0663 

1-076 

1 -0479 

10 

I  O529 

1-087 

1-085 

I  -0405 

1-0869 

1-0656 

1-0837 

1-097 

1-0605 

12 

1-0639 

1-0490 

1-1059 

1-0784 

1-1014 

I-II9 

1-0734 

14 

I-075I 

1-0577 

1-1257 

1-0912 

1-1196 

1*141 

1-0866 

16 

I-0863 

1-0663 

1-1463 

1-1043 

1-1380 

1-165 

1  -0999 

18 

1-0975 

1-0752 

1-1677  11175 

1-1570 

1-188 

1-1136 

20 

I-I087 

i-i'Si 

1-0843 
1-0934 

1-1902 

1-1306 

1-1765 

1-214 

1-1275 

zl 

I-I204 

1-2132 

1-1964 

1-242 

... 

24 

I-I322 

I-I026!  1-2372 

1-2169 

1-270 

26 

II44O 

I-1I20 

1-2620 

1-2379 

1-300 

;;; 

28 

I-I558 

ri2i6'  1-2876  ... 

1-2592 

I-330 

30 

1-1676 

1-292 

1-1318 

1-3140  ... 

1-2808 

1-362 

... 

32 

ri8oo 

1-1410 

1-3416!  ... 

x-3035 

1-395 

34 

1  •  1 924 

... 

1-1508 

1-3702  ... 

1-3268 

i-43i 

36 

1  -2048 

11608 

1-3996  ... 

^oS 

1-469 

38 

1-2172 

1-1709 

. . . 

1-3746 

1-500 

40 

1-2297 

1-422 

11811 

i-399i 

I-546 

42 

1-2427 

1-1914 

i-59i 

44 

1-2558 

1-2019 

... 

1-641 

46 

1-2690 

. . . 

1-2126 

. . . 

1-688 

48 

1-2822 

1-2231 

1736 

50 

1-2954 

1 -234c 

... 

1-785 

1 

546 


II.  TABLES. 


*2  Hi 

s  w 

n  *~ 

&° 

c  r!  -* 

NL- 

u  £  ^ 

*o  .  M 

— .  c  O* 

D  g  5 

<3  *e3 
Pi 

MS* 

i* 

1*  -  ■ 

M  h  *• 
0  « 

Nal 
per  cent, 
at  i9°5. 

•  51  0 

~ 

5 

i'°45 

I'045 

1*037 

I  -040 

— _ — 

I-035 

Q 

I  -03b 

I  '040 

„ 

1*035 

10 

1  "091 

1  009 

1  O50O 

1  '070 

I  OoO 

1  -072 

I  O7O 

1*082 

1*079 

lS 

1*137 

1  - 140 

1  - 1 1 6 

I  '  I  26 

1*113 

I  '  I  20 

1*128 

I'  124 

20 

I     I  OO 

1*195 

I  '  I  I  72 

1  159 

1*174 

1-156 

I  IOO 

1*179 

1*172 

25 

1-235 

1  "256 

I  IOl9 

1-207 

1*226 

1  -204 

I  ">  1  ft 

I  215 

1-234 

I  *224 

3° 

1*291 

1  321 

1*256 

tl/,(>T 

I  251 

1  254 

I  "27 1 

1-294 

I  260 

35 

1352 

1-309 

1*344 

1-309 

i*33i 

1*360 

i*344 

40 

1-420 

1-472 

1-2557 

1-366 

1-410 

1-368 

1*396 

1*432 

1414 

45 

1-488 

1  430 

1*483 

1-500 

1-566 

1-656 

1*500 

1*565 

1-580 

^546 

i*6oo 

1*575 

^5 

1-650 

... 

60 

1-740 

1-890 

... 

1*734 

1810 

1*777 

Table  of  Specific  Gravities  of  some  Acetates. 


Per 

Sodium 

Calcium 

Barium 

Lead 

Per 

Lead 

cent. 

Acetate. 

Acetate. 

Acetate. 

Acetate. 

cent. 

Acetat  _ . 

2 

I*0Il6 

1*0132 

1*0174 

TOI27 

32 

1*2395 

4 

IO232 

I  '0264 

IO348 

1*0255 

34 

1-2578 

6 

I*034I 

1*0362 

1-0500 

1-0336 

36 

1-2768 

8 

I*0439 

I  -0426 

I  -0628 

10520 

38 

1  -2966 

10 

I*0539 

I  0492 

1*0758 

1  0654 

40 

i*3*63 

12 

I  0644 

10562 

I  0902 

10796 

42 

1-3376 

14 

1*0750 

I  0632 

1  *  1 046 

1  0939 

44 

1*3588 

16 

10856 

10708 

II 20 1 

1-1054 

46 

13810 

18 

1*0910 

1*0792 

»'I363 

1  •  1 234 

48 

14043 

20 

1*1074 

1  0874 

ri522 

11384 

5o 

1-4271 

22 

1*1194 

10976 

I  *  1 694 

1*1544 

24 

1*1314 

1*1078 

1*1704 

26 

1-1440 

1*1139 

11 869 

28 

1*1572 

1*1307 

1  -2040 

30 

1*1706 

II426 

I  -2402 

I  '22 1  I 

Table  of  Specific  Gravities  and  per  cent.  Strengths  of 
Formic  Acid  at  15°  C. 


Specific 
Gravity. 

CH,0>. 

Specific 
Gravity. 

CH,0,. 

Specific 
Gravity. 

CH»02. 

I-025 

10 

II24 

50 

I-20I 

90 

1-053 

20 

1*142 

60 

1*223 

IOO 

ro8o 

30 

I*l6l 

70 

1*105 

40 

Il8o 

80 

547 


Appendix. 


Table  showing  the  Specific  Gravities  of  varying  strengths  of 
Alcohol  in  degrees  over  and  under  proof. 


Over  Proof. 

 ' 

Specific 
Gravity. 

Over  Proof. 

Specific 
Gravity. 

Under 
Proof. 

Specific 
Gravity. 

Per  cent. 

Per  cent. 



Per  cent. 

—  

67*0 

•8156 

28-0 

•8825 

8-o 

•9295 

65-0 

•8199 

27-0 

•8840 

9*0 

•9306 

64-6 

•8221 

26-0 

•8854 

io-o 

•9318 

63-I 

•8238 

25-0 

•8869 

no 

•9329 

62'0 

•8259 

24*0 

•8883 

I2'l 

'9MI 

6ri 

•8277 

23-0 

•8897 

131 

'9353 

6o-o 

•8298 

21*9 

•8912 

14-2 

•9364 

59' 1 

•8315 

209 

•8926 

15*3 

•9376 

58-0 

•8336 

19-9 

•8940 

16-0 

■9384 

57'1 

•8354 

19-1 

•8951 

17-1 

•9396 

56-0 

•8376 

18-0 

•8966 

18-2 

•9407 

55"° 

•8366 

16-9 

•8981 

x9'3 

•9419 

54* 1 

•8413 

159 

•8996 
•9008 

20 -o 

•9426 

S3'1 

•8431 
•8448 

15-0 

21'2 

'9437 

521 

I3'9 

•9023 

22'2 

•9448 

51'1 

•8465 

131 

•9034 

23*1 

'9456 

50-1 

•8482 

120 

•9049 

23*9 

•9464 

49' 1 

•8499 

in 

•9060 

25-I 

•9476 

48-0 

•8516 

IO'O 

•9075 

26"3 

•9488 

47'° 

•8533 

8-9 

•9089 

27-I 

•9496 

46-0 

•8550 

8-o 

•9  IOC 

28-0 

'95°3 

45'° 

•8566 

7-1 

•91 1 1 

29- 2 

'95l5 

43'9 

•8583 

5'9 

•9126 

30-I 

•9522 

43'1 

•8597 

5'° 

•9137 

35' 1 

'9565 

42-0 

•8615 

3'9 

•9152 

40*1 

•9603 

4I-.I 

•8629 

3-o 

•9163 
•9178 

45'o 

•9638 

40-0 

•8646 

19 

5o-3 

•9674 

39'i 

•8660 

rp 

•9189 

54'8 

•9701 

38-0 

•8678 

Proof  spirit 

•9200 

60-4 

'9734 

37'i 

•8692 

653 

•9762 

35-9 

•8709 

Under  proof 

70-1 

•9790 

35-o 

•8723 

1*3 

•9214 

75'4 

•9822 

34-i 

•8737 

2'2 

•9226 

80-4 

•9854 

32-9 

•8755 

31 

•9237 

85-2 

•9886 

32-0 

•8769 

4-0 

•9248 

90-2 

•9922 

310 

•8783 

5*o 

•9259 

95'4 

•9962 

300 

•8797 

60 

•9270 

1000 

10 

29-0 

•881 1 

7-0 

•9282 

548 


II.  TABLES. 


Table  for  the  Reduction  of  Hydrometer  Degrees  into 
Specific  Gravities  (Gerlach). 

A.  For  liquids  lighter  than  water  at  12-5°  C. 


Degs. 

Beaune. 

Cartier. 

Beck. 

Degs. 

Beaune. 

Cartier. 

Beck. 

O 

roooo 

• 

31 

•8742 

: 

•8707 

•8457 

I 

•9941 

32 

•S690 

•S652 

■8415 

2 

... 

•9833 

33 

•8639 

■8598 

•8374 

3 

... 

•9826 

34 

•8588 

•8545 

•8333 

4 

•9770 

35 

•8538 

•8491 

•8292 

5 

... 

•97M 

36 

•8488 

•8439 

•8252 

6 

... 

... 

•9659 

37 

•8439 

•8387 

•8212 

7 

... 

•9604 

38 

•8391 

•8336 

•8173 

8 

... 

•9550 

39 

•8343 

•8286 

•8l33 

9 

•9497 

40 

•8295 

•8095 

10 

1  OOOO 

•9444 

41 

•8249 

•8061 

1 1 

■9932 

•9392 

42 

•8202 

•8018 

12 

•9865 

•9340 

43 

•8156 

7981 

13 

•9799 

•9764 

•9289 

44 

•81 1 1 

7944 

14 

•9733 

•9239 

45 

•8066 

•7907 

15 

•9669 

•9695 

•9189 

46 

•8022 

•7871 

16 

•9605 

•9627 

•9159 

47 

7978 

... 

7834 

•7 

•9542 

•9560 

•9090 

48 

7935 

•7790 

18 

•9480 

•9493 

•9042 

49 

•7892 

7763 

19 

•9420 

•9427 

•8994 

50 

•7849 

7727 

20 

•9359 

•9363 

•8947 

5i 

7807 

•7692 

21 

•93OO 

•9299 

•8900 

52 

•7766 

7658 

22 

•924I 

•9237 

53 

7725 

•7623 

23 

•9183 

•9175 

•8808 

54 

•7684 

7589 

24 

•9125 

•9114 

•8762 

55 

7643 

7556 

25 

•9068 

•9054 

•8777 

56 

•7604 

7523 

26 

•9OI2 

•8994 

•8673 

57 

7565 

7489 

27 

•8957 

•8935 

•8627 

58 

•7526 

•7456 

28 

•8902 

•8877 

•8585 

59 

7487 

7423 

29 

•8848 

•882O 

•8542 

60 

7449 

•7391 

30 

•8795 

•8763 

•8500 

Specific  Gravities  of  Caustic  Alkali  Solutions. 


Per  Cent. 

NH3. 

KHO. 

NaHO. 

Per  Cent. 

KHO. 



NaHO. 

I 

•9959 

1009 

I  OI 2 

36 

1-361 

i\395 

2 

•9915 

1017 

I  O24 

37 

i'374 

1-405 

3 

•9873 

1-025 

I  O35 

38 

1387 

4 

•9831 

I  033 

I  -046 

39 

1-400 

1*426 

549 


APPENDIX. 


Specific  Gravities  of  Caustic  Alkali  Solution  (Continued). 


i  er  Leni, 



IN  ri... 



1/  [in 

Nal  IO. 

Per  Cent. 

KHO. 

NaH. 

c 
j 

I  'O41 

I  058 

/IO 

4U 

 <— 

I  '41 2 

1  'A  77 

1  40/ 

6 

*Q7AO 
y/4w 

I'OAQ 

I  -070 

A  T 

41 

I  *A2C 
1  4^3 

T  */L/17 
1  44/ 

7 

'Q70Q 
yi^y 

1-058 

1*081 

A2  . 

1  40" 

I  'AC.7 
1  4  j  / 

8 

•q67o 

I  "065 

1*092 

/t  7 
40 

1  4jw 

1-468 

o 

y 

T  •_07/t 

T  •  IA1 
1  lUj 

44 

I  '462 

T-/I78 
1  47O 

10 

•QCQ7 

yjyo 

i-o8^ 

t  •  t  t  rr 

1   1  1D 

A  C 

43 

T  *A7  C 
1  4/  D 

1-488 

1 1 

*CK  C.6 

I  "092 

I  '  I  26 

/16 
4U 

1-488 

T  */l  QQ 
1  ^yy 

1 2 

•n  C20 

I '  IOI 

T  *  T  17 

A  7 

t  '/inn 
1  4yy 

i  •  con 

1  Duy 

'0184. 

1*1  10 

I*I48 

4.8 

4° 

I  •  C  T  f 

I  •C.  IQ 

y44y 

1  1  iy 

T  •  t  cn 

49 

T  •  CO  C 

i  •  con 
1  b-^9 

I  c 

y4"-4 

I-I28 

1  ■  1 7© 

CO 

I  •  C  7Q 

1  jJy 

1  *  C/IO 
A  J4U 

16 

•0380 
y^ou 

T'l  77 

i'i8i 

C  T 

T  '  C  C  O 

T  •  C  CO 

1  bbu 

I  7 

yj4/ 

I"I46 

I  - 1 92 

CO 

t  *c6c 

1  bub 

1  -560 

18 

9ja4 

T  •  T  C  C 

I  '202 

bo 

1  b/° 

T  *  C70 
1  b/u 

IQ 

•Q28^ 

Il66 

1*217 
1  _  1  j 

C/l 

T  *COO 

1  ^ou 

20 

•Q2C  I 

1*177 
1  1  /  / 

I  "22C 

1  '604 

1  "COT 
1  Dyi 

21 

•9221 

ri88 

I  *2l6 

c6 

1*618 

I  *6oi 

22 

•QTQI 
yiy  1 

1*198 

T  2/1 7 

C  7 

01 

t  '670 

i  *6 1 1 

o  -> 
-J 

'9162 

1  '209 

I*258 

c8 

I  '642 

1  '622 

24. 

•Q1 11 

1*220 

1*269 

Co 

jy 

i*6ct( 

1  Jj 

1-677 

2< 

J 

•9IO6 

I  "270 

60 

1*667 

T  'f\A  7 

26  5 

•Q078 

I  *24I 

I  '290 

61 

i*68i 

t  *6ca 

1  u  j4 

27 

•QOC2 

I  "252 

62 

1  *6oc 
1  uyj 

I  "664 

28 

'9026 

I  "264 

I  '310 

6i 
uj 

T  *70C 

I  "67A 

29 

•9OOI 

1*276 

1321 

64 

1*718 

1-684 

30 

8976 

1*288 

1-332 

65 

1729 

1*695 

31 

•8953 

I-300 

i'343 

66 

1-740 

I*705 

32 

•8929 

I-3II 

i'353 

67 

1754 

1715 

33 

•8907 

1-324 

1-363 

68 

1-768 

1*726 

34 

•8885 

I-336 

1-374 

69 

1-780 

1-737 

35 

•8864 

1-349 

1-384 

70 

1790 

1*748 

Sulphurous  Acid. 

Quantities  of  Anhydrous  Sulphurous  Acid  in  Solutions  of  different 
Densities.  F.  Authon. 


Specific 

Anhydrous 

Specific 

Anhydrous 

Specific 

Anhydrous 

Gravity. 

Acid  in  100. 

Gravity. 

Acid  in  iod. 

Gravity. 

Acid  in  100. 

1-046 

9-54 

1-023 

5-72 

1036 

8-59 

IOI3 

2*86 

1-031 

7-63 

ro2o 

4-77 

1*009 

I90 

1-027 

6-68 

1*016 

3-82 

1-005 

o-95 

55° 


II.  TABLES. 


Sulphuric  Acid. 

Quantities  of  Liquid  and  Anhydrous  Acid  in  Mixtures  of  Sulphuric 
Acid  and  Water  at  different  Densities. 


Anhy- 

Anhy- 

■2  4 

Anhy- 

•fi 

8 

Spcci  fic 

•oM2 

Specific 

Gravity. 

'm-  •  a  \ 

acid 

Gravity. 

acid  in 

Gravity. 

■0  M  m 

—  •'  c 

acid  in 

a*  mi 
J  d, 

CO  _ 

in  100. 

100. 

100. 

18485 

IOO 

8i-54 

I-5503 

66 

5382 

1-2409 

33 

269 1 

1-8475 

99 

80-72 

I-5390 

65 

5330 

1  2334 

32 

26-09 

I  -8460 

98 

79-90 

15280 

64 

52-18 

I-226o 

3i 

25-28 

1-8439 

97 

7909 

I-5170 

63 

5i-37 

1-2184 

30 

2446 

1-8410 

96 

78-28 

1-5066 

62 

5o-55 

1  2I08 

29 

23-65 

1-8376 

95 

77-46 

I  -4960 

61 

49  74 

1  2032 
1-1956 

28 

22-83 

I-8336 

94 

7665 

I  -4860 

60 

48-92 

27 

22-OI 

1-8290 

93 

75-83 

1-4760 

59 

48- 1 1 

1-1876 

26 

2T20 

1-8233 

92 

75-02 

I  -4660 

58 

47  29 

I-I792 

25 

2038 

1-8179 

91 

74.20 

14560 

57 

46-48 

1  •  1 706 

24 

1957 

I-8II5 

90 

73-39 

I  -4460 

56 

45-66 

ri626 

23 

1875 

1-8043 

89 

72.57 

1  4360 

55 

44-85 

11549 

22 

17-94 

1-7962 

88 

7175 

1-4265 

54 

4403 

1-1480 

21 

1712 

1-7870 

87 

70-94 

1-4170 

53 

43-22 

I-I4IO 

20 

163I 

1-7774 

86 

70-12 

I-4073 

52 

4240 

1I330 

19 

15  49 

1-7673 

85 

69-31 
68-49 

1-3977 

5i 

41-58 

i  I  I246 

18 

I468 

1-7570 

84 

1-3884 

50 

4077 

II 165 

17 

I386 

I-7465 

83 

67-68 

1-3788 

49 

3995 

I  •  1 090 

16 

I305 

1-7360 

82 

66-86 

1-3697 

48 

39-14 

1-1019 

15 

1223 

I-7245 

81 

6605 

1-3612 

47 

38-32 

1  0953 

H 

lr4I 

17 100 

80 

65-23 

1-3530 

46 

37-51 

10887 

13 

IO-6o 

1  6993 

79 

64-42 

1-3440 

45 

3669 

1  0809 

12 

978 

1-6870 

78 

63-60 

1-3345 

44 

35-88 

I-Q743 

11 

8-97 

1-6750 

77 

62-78 

I-3255 

43 

35o6 

1  -0682 

10 

815 

1-6630 

76 

61-97 

1-3165 

42 

3425 

10614 

9 

7-34 

1-6520 

75 

61-15 

13080 

41 

I  3343 

1-0544 

8 

652 

1-6415 

74 

60-34 

1-2999 

40 

3261 

1  0477 

7 

571 

1-6321 

73 

!  59-52 

12913 

39 

1  3180 

1  -0405 

6 

489 

1-6204 

72 

i  5871 

1-2826 

38 

:  30-98 

1-0336 

5 

4-08 

1-6090 

7i 

|  57-89 

1-2740 

37 

30- 17 

1  -0268 

4 

326 

1-5975 

70 

57-o8 

1-2654 

36 

29-35 

1  -0206 

i  3 

2-45 

1-5868 

69 

5626 

1-2572 

35 

28-54 

10140 

I  2 

163 

1-5760 

68 

55-45 

1-2490 

34 

27-72 

10074 

•82 

1-5648 

67 

54-63 

I 

55' 


APPENDIX. 


Nitric  Acid. 

Quantities  of  Liquid  and  of  Anhydrous  Acid  contained  in  Mixtures  of 
Nitric  Acid  and  Water  at  different  Densities  (Ure — 6o°  F.). 


Specific 
gravity. 

Liquid 
acid, 
sp.gr. 

in  100. 

Anhy- 
drous 
acid 
in  ico. 

'  

Specific 
gravity. 

Liquid 
acid, 
sp.gr. 

1*5, 
in  100. 

Anhy- 
drous 
acid 

in  1:0. 

Specific 
gravity. 

Liquid 
acid, 
sp.gr. 

1 '5, 
in  100. 

Anhy. 
drous 
acid 
in  100. 

I  •  KCO 

IOO 

70'7OO 
1  y  1 

1^78 
*■  j/" 

66 



52-602 



1-189 

22 
jj 



26*301 

I  '4q8 

00 

1&Q02 
/     .7  j 

i'27 2 

65 

5l-8o5 
j  *  j 

1-183 

22 
J 

2^'KOA 

i  -406 

q8 

y 

78-I06 

1-368 

64 

5 1  -068 

ri77 

21 

J 

2A'707 

I  '404 

07 
y  1 

77*^.00 

1  Jw  J 

63 

50*21 1 

1*171 

^O 

2l'QOO 

I  '401 

Q6 

76**;i2 

1-358 

62 

4Q'4I4 

17  ft 

1*165 

20 
^■y 

2TI  I  2 
j     1 J 

I-488 

QC 

7^-7i 
1  j  1 1  j 

I  *  2C  2 

61 

48-6I7 

1*1  KQ 

28 

22*^l6 

r48i; 

04 

74-Q18 

I"U8 

60 

47-820 

I  ■  I  c  -3 

27 

2  I  "57Q 

j  J  y 

1-482 

93 
yj 

74T2I 

r"343 

59 

47-023 

1*146 

26 

20*722 

I'479 

02 

y 

7V  2.24 

/  J  J  r 

1 338 

JJ 

58 

46-226 

1*14 

25 
J 

10*02-; 

r476 

y 

72-527 

1*332 

JJ 

57 

45-429 

1*134 

24 

19*128 

r473 

90 

7I-730 

1-327 

56 

44-632 

1*129 

23 
J 

18331 

jj 

I-470 

8o 

7o-q^^ 

1*322 

55 

43*835 

Tj       J  J 

I' 122 

22 

17*-;  34 

1  /  JJT 

r467 

88 
87 

70-1 26 

I*3l6 

J 

^4 

JT- 

43*038 

tJ  ^S) 

1*117 

21 

l6'737 

I'464 

6q"?3q 
y  jj7 

I  •  -2  I  I 

J 

^3 

JJ 

42-241 

1*111 

20 

I  'Q40 

r460 

86 

68-542 

I"  306 

J 

52 

J 

41'444 

1-105 

J 

10 

i  -;'i43 

r457 

85 

67-745 

1-300 

51 

40-647 

1099 

18 

14346 

l'A^2 

84 

66-048 

I'2Q5 

^0 

J 

3Q-850 

J7  J 

roQ^ 

7J 

17 

I  3*-;4Q 
1 3  jty 

I-450 

83 

66-155 

I-28o 

49 

39-053 

I*088 

16 

I2-752 

r446 

82 

65-354 

I-283 

48 

38^56 

r082 

15 

"•955 

I  442 

8l 

64-557 

1-276 

47 

37'459 

r076 

*4 

IPI58 

80 

63-760 

1-270 

46 

36662 

I-07I 

13 

IO361 

1 '435 

79 

62-963 

1-264 

45 

35-865 

1-065 

12 

9'564 

i-43i 

78 

62-I66 

I-258 

44 

35-068 

I-059 

1 1 

8*767 

1-427 

77 

61-639 

I-252 

43 

34-271 

I-054 

10 

7*970 

1-423 

76 

60'572 

1-246 

42 

33-474 

I-048 

9 

7-173 

1-419 

75 

59-775 

I-240 

4i 

32-677 

I  O43 

8 

6376 

i'4i5 

74 

58-978 

1-234 

40 

31-880 

I-037 

7 

5-579 

141 1 

73 

58-I8I 

1-228 

39 

31-083 

IO3  2 

6 

4782 

1406 

72 

57^84 

T22I 

38 

30-286 

I'027 

5 

3-985 

1402 

7i 

56  587 

1-215 

37 

29-489 

I  02 1 

4 

3-i88 

1-398 

70 

55-790 

I-208 

36 

28-692 

IOl6 

3 

2*391 

1-395 

69 

54-993 

1-202 

35 

27-895 

roii 

2 

1-594 

1-388 

68 

54-I96 

1-196 

34 

27-098 

1*005 

1 

o-797 

1-383 

67 

53'399 

552 


1 1.  TABLES. 


Hydrochloric  Acid. 


Quantities!  oil  Liquid  and  of  Anhydrous  Acid  and  of  Chlorine  in  Mix- 
tures of  Hydrochloric  Acid  and  Water  at  different  Densities. 


I  iquid 

H.  CI. 

1  Liquid 

Specific 

Acid, 

CI. 

Spcci  fic 

Acid, 

j  H.  CI. 

CI. 

( i  ravity. 

sp.gr.  1  "20 
in  100. 

in  100. 

in  100. 

( iravitv. 

sp.gr.  1  '20 
in  100. 

in  100. 

1 

I  "2000 

100 

40-777 

39*675 

i* 1000 

50 

1 

'  20*388 

19-837 

1-1982 

99 

40-369 

39*278 

1  "0980 

49 

19*980 

19*440 

I  '1964 

98 

39-961 

38-882 
38-485 

1  "0960 

48 

*9'572 

19*044 

1-1946 

97 

39'554 

1*0939 

47 

19*165 

18*647 

1-1928 

96 

39'46 

38-089 

1*0919 

46 

'8*757 

18*250 

1-1910 

95 

38*738 

37-692 

1*0899 

45 

'  -8*349 

17*854 

1-1893 

94 

38  '330 

37-296 

1*0879 

44 

17*941 

'7'457 

fi87s 

93 

37"923 

36*900 

1*0859 

43 

'7*534 

17*060 

1-1857 

92 

37*5*6 

36'503 

1  '0838 

42 

17*126 

16*664 

1-1846 

91 

37-108 

36*107 

i*o8i8 

4' 

16*718 

16-217 

1-1822 

90 

36*700 

35'707 

1*0798 

40 

16*310 

15-870 

1-1802 

89 

36*292 

35*3*0 

1*0778 

39 

15*902 

15-474 

1-1782 

88 

35-884 

34*9X3 

1*0758 

38 

'5*494 

1 5"°77 

1-1762 

87 

35*476 

34'5'7 

1*0738 

37 

15*087 

14.680 

1*1741 

86 

35-o68 

34*121 

1*0718 

36 

14*679 

14*284 

1-1721 

85 

34*  660 

33*724 

1  '0697 

35 

14*212 

13*887 

1*1701 

84 

34*252 

33*328 

1*0677 

34 

13*863 

i3'49o 

1-1681 

23 

33'845 

32*93' 

1*0657 

33 

'3*456 

I3'°94 

Ti66i 

82 

33*437 

32-535 

1  "0637 

32 

'  3*049 

12*697 

1*1 64 1 

81 

33'o27 

32*136 

1*0617 

31 

12*641 

12*300 

1  *  1620 

80 

32*621 

3''746 

1*0597 

30 

12*230 

1 1  '903 

1-1599 

79 

32-213 

3**343 

1*0577 

29 

11*825 

1 1*506 

1 -1578 

78 

31*805 

30*946 

1  *°557 

28 

1 1  *4 1 8 

11*109 

i"i557 

77 

31-398 

30*550 

'  '0537 

27 

I  I'OIO 

10*712 

'*'537 

76 

30*990 
30-582 

30-I53 

1*0517 

26 

10*602 

10*316 

75 

29*757 

1  0497 

25 

10*194 

9*919 

1*1494 

74 

3o-i74 

29*361 

1*0477 

24 

9*786 

9-522 

'"'473 

73 

29-767 

28*964 

*'0457 

23 

9*379 

9*136 

72 

29*359 

28*567 

''o437 

22 

8*971 

8-729 

'*i43' 

7i 

28-951 

28*171 

1  -04 1 7 

8*563 

8*332 

1  '1410 

70 

28-544 

27*772 

'-°397 

20 

8'i55 

7*935 

1-1389 

69 

28-136 

27*736 

'"0377 

'9 

7*747 

7*53? 

1-1369 

68 

27*728 

26*979 

*'0357 

18 

7*34° 

7*141 

'''349 

67 

27-321 

26*583 

'"0337 

.7 

6*932 

6*74- 

1-1328 

65 

26-913 

26-186 

1*0318 

.6 

6-524 

6*343 

1-1308 

65 

26-505 

25'789 

1*0298 

•5 

6'n6 

5*95« 

1-1287 

64 

26*098 

25-392 

1  -0279 

14 

5'709 

5*554 

1  1267 

63 

25*690 

24'996 

1*0259 

13 

5'3°» 

5*'58 

1  -1247 

62 

25-282 

24*599 

1  '0239 

12 

4-893 

4*762 

1 '1226 

61 

24-874 

24*202 

I  *0220 

1 1 

4*486 

4-362 

1  'I2C6 

60 

24*466 

23-805 

I  "02C>0 

10 

4*078 

3-968 

1-1185 

59 

24*058 

a  ;  "4< 

I  *OI  80 

9 

3-670 

3*571 

1-1.64 

58 

23-650 

23*012 

1*0160 

8 

3*262 

3'74 

i'«43 

57 

23*242 

22*615 

I  0140 

7 

2*854 

2*778 

I'II23 

56 

22*834 

22'2l8 

I  '0I20 

6 

2*447 

2'?8l 

1  *i  102 

55 

22*426 

21-822 

i'oioo 

5 

2-039 

1-984 

1*1082 

54 

22*019 

21*425 

1  *oo8o 

4 

1 -63 1 

1-588 

i'io6i 

53 

2l"6ll 

2I*028 

i  "0060 

1 

1*224 

1*191 

1  "1041 

52 

21-203 

20*632 

1  0040 

2 

o*8i6 

o*795 

1 " 1020 

5i 

20*796 

20*236 

1*0020 

0*408 

o*397 

553 


APPENDIX. 


Acetic  Acid. 

Quantities  of  Crystallisable  Acid  in  Mixtures  of  Acetic  Acid  and 
Water  of  various  Densities  at  150  C. 


Pa  rts  of 

Parts  of 

Parts  of 

3arts  of 

Crystal- 
li  sable 
Acid  in 

Specific 
Gravity. 

Crystal- 
lisable 
Acid  in 

Specific 
Gravity. 

Crystal- 
lisable 
Acid  in 

Specific 
Gravity. 

Crystal- 
lisable 
Acid  in 

Specific 
Gravity. 

100. 

ICO. 

ICO. 



100. 

100 

i'°553 

75 

1*0746 

5° 

1*0615 

25 

"4*0350 

99 

1*0580 

74 

I-C744 

49 

1*0607 

24 

1 '0337 

98 

1*0604 

73 

1*0742 

48 

1*0598 

23 

1*0324 

97 

1*0625 

72 

1*0740 

47 

1*0589 

22 

1*0311 

96 

1*0644 

71 

1*0737 

46 

1*0580 

21 

1*0298 

95 

1*0660 

70 

I-°733 

45 

1*0571 

20 

1*0284 

94 

1*0674 

69 

1*0729 

44 

1  '0562 

J9 

1*0270 

93 

1*0686 

68 

1*0725 

43 

1*0552 

18 

1*0256 

92 

1  "0696 

67 

1*0721 

42 

1 'o543 

17 

1*0242 

91 

1*0705 

66 

1*0717 

4i 

i'Q533 

16 

1*0228 

90 

1*0713 

65 

1*0712 

40 

1*0523 

15 

1  '0214 

89 

1*0720 

64 

1*0707 

39 

1*0513 

I  *020I 

88 

1*0726 

63 

1  '0702 

38 

1  0502 

13 

I  OI05 

87 

1*0731 

62 

1*0697 

37 

1*0492 

12 

I  'OI7I 

86 

1*0736 

61 

i'o69i 

36 

1*0481 

I*OI57 

85 

60 

1*0685 

1  '0470 

10 

84 

1*0742 

59 

1*0679 

34 

1*0459 

9 

l*OI27 

83 

I-°744 

58 

1*0673 

33 

1  -0447 

8 

I*OII3 

82 

;  1*0746 

57 

1*0666 

32 

1*0436 

7 

I  '0098 

81 

;    1  "0747 

56 

1  *o66o 

31 

1  0424 

6 

1*0083 

80 

1*0748 

55 

1*0653 

3° 

1*0412 

5 

1  '0067 

79 

1*0748 

54 

1  "0646 

29 

1  '0400 

4 

I  *0052 

78 

1*0748 

53 

1*0638 

28 

1*0388 

3 

I*0037 

77 

1*0748 

52 

1*0631 

27 

1 '0375 

2 

I  "0022 

76 

1*0747 

5i 

1*0623 

26 

1*0363 

1 

I  "0007 

N.B.— The  density  of  the  mixture  increases  until  nearly  25%  of  water  is 
present,  after  which  it  again  decreases.  Acetic  Acid  is  therefore  better  tested 
volumetrically  with  a  standard  solution  of  alkali. 


Table  of  Solubilities  of  various  Acids  in  100  parts  of  Water 
  at  various  Temperatures.  


Tempera- 

Benzoic 

Boric  Acid. 

Oxalic 

Tartaric 

Ammonia 

ture. 

Acid. 

Cryst. 

Anhyd. 

Acid. 

Acid. 

Alum. 

0 

i*9 

ri 

5'2 

115*0 

5'2 

IO 

•21 

2*9 

i*6 

8*o 

120*0 

9*2 

20 

4*0 

2*3 

i3'9 

1390 

137 

30 

•42 

... 

23*0 

1560 

19-3 

40 

•55 

7*0 

39 

35'0 

176*0 

273 

50 

51-2 

195*0 

36-5 

60 

1*2 

1 1"0 

6*'i 

75° 

217  O 

51-3 

70 

1*8 

1 1 8*o 

244*0 

72*0 

80 

1 6*8 

95 

205*0 

273*0 

103*0 

90 

345-o 

307*0 

1 88*o 

IOO 

59 

290 

16*0 

i  

3430 

422*0 

1   

554 


II.  TABLES. 


Thermometer  Table  showing  the  comparison  of  degrees  of 
Centigrade,  Reaumur,  and  Fahrenheit  


c  1 

I 

r . 

C. 

■ 

IV. 



C. 

R. 

w 
r . 

 1 

100 



80 

212 

56 

44*8 

132-8 

12 

9-6 

53*6 

99 

79-2 

210*2 

55 

44 

131 

1 1 

8-8 

51*8 

98 

78-4 

2o8'4 

54 

43*2 

129-2 

10 

8 

50 

97 
96 

77*6 

206-6 

53 

42-4 

127-4 

9 

7-2 

48-2 

76-8 

204*8 

52 

41-6 

125-6 

8 

64 

46-4 

95 

76 

203 

51 

40-8 

123-8 

7 

5*6 

44*6 

94 

75'2 

20T2 

50 

40 

122 

6 

4-8 

42-8 

93 

74*4 

199*4 

49 

39*2 

I20'2 

5 

4 

41 

92 

73*6 

I97.6 

48 

38*4 

118-4 

4  1 

3*2 

39*2 

91 

72-8 

195*8 

47 

37*6 

n6-6 

3 

2-4 

37*4 

90 

72 

194 

46 

36-8 

114-8 

2 

16 

35*6 

89 

71*2 

192*2 

45 

36 

113 

1 

08 

33*8 

88 

70-4 

190-4 

44 

35*2 

I  I  1*2 

0 

0 

32 

87 

69-6 

188-6 

43 

34*4 

109-4 

-  1 

-  o-8 

30-2 

86 

68-8 

186-8 

42 

33*6 

IO76 

—  2 

-  16 

28-4 

85 

68 

185 

4i 

32-8 

105-8 

3 

-  2-4 

266 

84 

67-2 

1832 

40 

32 

104 

-  4 

-  3*2 

24-S 

83 

66-4 

181-4 

39 

312 

102-2 

-  5 

-  4 

23 

82 

65-6 

179-6 

38 

3°*4 

IOO-4 

-  6 

-  48 

2T2 

81 

64-8 

177-8 

37 

296 

98-6 

-  7 

-  56 

I94 

80 

64 

176 

36 

28-8 

96-8 

-  8 

-  64 

I7.6 

79 

63-2 

174-2 

35 

28 

95 

-  9 

-  7-2 

•5*8 

78 

62*4 

172-4 

34 

27-2 

93*2 

-10 

-  8 

14 

77 

6r6 

170-6 

33 

26-4 

914 

-  1 1 

-  8-8 

I2'2 

76 

60.8 

1688 

32 

256 

896 

— 12 

-  9*6 

IO*4 

75 

60 

167 

31 

24-8 

87-8 

-13 

— 104 

8-6 

74 

59"2 

165-2 

30 

24 

86 

-14 

—  11*2 

68 

73 

58-4 

163*4 

29 

23-2 

84-2 

-15 

-12 

5 

72 

57*6 

1616 

28 

224 

82-4 

-16 

-128 

3*2 

71 

568 

159*8 

27 

216 

806 

-*7 

-136 

i*4 

70 

56 

158 

26 

208 

78-8 

-18 

- 144 

-  0-4 

69 

55'2 

156-2 

25 

20 

77 

-  19 

-152 

_  2-2 

68 

54'4 

154*4 

24 

192 

75*2 

-20 

-16 

-  4 

67 

53*6 

1526 

23 

18-4 

73*4 

-21 

-16-8 

-  5*8 

66 

52-8 

150-8 

22 

176 

716 

-22 

-176 

-  7*6 

65 

52 

149 

21 

168 

698 

-23 

-185 

-  9-4 

64 

51-2 

147-2 

20 

16 

68 

-24 

l  -19-2 

—  I  I  '2 

63 

504 

145*4 

19 

15*2 

66-2 

-25 

-20 

— 13 

62 

49*6 

143*6 

18 

144 

644 

-26 

—  20-8 

—  14S 

61 

48-8 

1418 

17 

136 

626 

-27 

—  21-6 

-166 

60 

48 

140 

16 

128 

608 

-28 

—  22-4 

— 18*4 

59 

47-2 

138-2 

15 

12 

59 

-29 

-232 

—  20-2 

58 

46-4 

1364 

14 

I  1-2 

57*2 

-30 

-24 

-22 

57 

45-6 

1346 

13 

104 

55*4 

1 

555 


APPENDIX. 


Table  of  conversion  of  Fahrenheit,  Centigrade,  and 
Reaumur. 


F. 

C. 

R. 

F. 

C. 

.-  - 

R. 

F. 

c. 

R. 

+  212 

+ 100 

+  80 

170 

76-67 

6 1  33 

128 

53-33 

42-67 

21 1 

99-4 

79-56 

169 

76-1 1 

60-89 

127 

52-78 

42-22 

2IO 

98-89 

79-11 

168 

75-55 

60*44 

126 

52-22 

41-78 

209 

98"33 

78-67 

167 

75 

60 

125 

51-67 

41-33 

'208 

97-78 

78-22 

166 

74-44 

59-56 

124 

5111 

40-89 

207 

97-22 

77-78 

165 

73-89 

59" 

123 

50-55 

40-44 

206 

96-67 

77-33 

164 

7333 

58-67 

122 

50 

40 

205 

96  1 1 

76-89 

163 

72-78 

58*22 

121 

49-44 

39-56 

204 

9555 

76-44 

162 

72-22 

57-78 

120 

48-89 

39-11 

203 

95 

76 

161 

71-67 

57-33 

119 

48-33 

38-67 

202 

94*44 

75-56 

160 

7111 

56-89 

1 18 

4778 

38-22 

201 

93 '89 

75" 

159 

70-55 

56-44 

117 

47-22 

37-78 

200 

93*33 

74-67 

158 

70 

56 

1 16 

46-67 

37-33 

199 

9278 

74-22 

157 

69-44 

55*56 

"5 

46- 1 1 

36-89 

198 

92-22 

73-78 

156 

68-89 

114 

45-55 

36-44 

197 

91-67 

73*33 

155 

68-33 

54-67 

113 

45 

36 

196 

91*11 

72-89 

154 

67-78 

54-22 

1 12 

44-44 

35'56 

195 

90-55 

72-44 

153 

67-22 

53-78 

in 

43-89 

35-n 

194 

90 

72 

152 

66-67 

53-33 

no 

43'33 

34-67 

193 

89-44 

7I-56 

151 

66-ii 

52-89 

109 

42-78 

34-22 

192 

88-89 

71-11 

150 

65-55 

52-44 

108 

42-22 

33-78 

191 

88'33 

70-67 

149 

65 

52 

107 

41-67 

33-33 

190 

8778 

70-22 

148 

64-44 

5 --56 

106 

41-11 

32-89 

189 

87-22 

6978 

147 

63-89 

51-11 

105 

40-55 

32-44 

188 

86-67 

69-33 

146 

63-33 

50-67 

104 

40 

32 

187 

86-n 

68-89 

H5 

62.78 

50-22 

103 

39-44 

31*56 

186 

85-55 

68-44 

144 

62-22 

49-78 

102 

38-89 

3m 

185 

85 

68 

H3 

61-67 

49-33 

101 

38-33 

30-67 

184 

84-44 

67-56 

142 

6i-ii 

4s  09 

100 

37-78 

30-22 

183 

83-89 

67-11 

141 

60-55 

4844 

99 

37*22 

2978 

182 

83-33 

66-67 

140 

60 

48 

98 

36-67 

29-33 

181 

82-78 

66*22 

139 

59'44 

47  56 

97 

36-11 

28*89 

180 

82-22 

6578 

138 

58-89 

47  11 

96 

35'55 

28-44 

179 

81-67 

6c— 2 
°5  j3 

T  -5*7 
l37 

c8-->t 

95 

35 

28 

I78 

8rn 

64-89 

136 

5778 

46-22 

94 

34*44 

27-56 

177 

8o-55 

64-44 

135 

57-22 

45-78 

93 

33;89 

27 '  1 1 

176 

80 

64 

134 

56-67 

45-33 

92 

33-33 

26-67 

175 

79'44 

63  56 

133 

56-11 

44.89 

9i 

32-78 

26-22 

i74 

78-89 

63- 1 1 

132 

55-55 

44-44 

90 

32-22 

2578 

173 

78-33 

62-67 

131 

55 

44 

89 

31-67 

25*33 

172 

7778 

62-22 

130 

54-44 

43-56 

88 
87 

31*11 

24-89 

171 

77-22 

6178 

129 

53-89 

43-n 

30-55 

24-44 

556 


ii.  TABLES. 


Table  of  conversion  of  Fahrenheit,  Centigrade,  and 

Reaumur— continued. 


F.  1 

C.  ' 

R. 

F. 

c. 

R  1 
1 

F. 

C. 

' 

R. 

86 

30 

24 

: 

43 

61  ] 

4-89 

I  | 

—  17-22 

-13-78 

84  i 

29-44  | 

23-56 

42 

555 

4-44 

O 

-1778 

—  14-22 

28-89 

23-11 

41 

5 

4 

—  1 

-18-33 

-14-67 

83  1 

28-33  i 

22-67 

40 

4-44 

356 

—  2 

—  18-89 

-I5-II 

82 

27-78 

22-22 

39 

5/89 

311 

1 
J 

—  1944 

-«5-56 

Si 

27  22 

2178 

38  \ 

3'33 

2-67 

—  4 

-20 

16 

80 

26-67 

21-33 

37  : 

2-78 

222 

5  : 

-20-55 

—  1644 

79 

26- 1 1 

2089 

36 

2-22 

i-78 

-  6 

— 2  in 

—  16-89 

78 

25-55 

20-44 

35 

1-67 

.  l-33 

-  7 

— 2167 

-17-33 

77 

25 

20 

34 

111 

0-89 

—  8 

—22-22 

-17-78 

76 

24-44 

19-56 

33 

o-55 

0-40 

—  9 

—22-78 

—  18-22 

75  ; 

23-89 

19-11 

32 

0 

0 

-10 

—23-33 

-18-67 

74 

23-33 

18-67 

31  ! 

-  0  55  ! 

—  0-40 

—  1 1 

—23J9 

—  I9-II 

73 

2278 

18-22 

30  1 

i-n 

—  089 

—  12 

—  24-44 

-  I9-56 

72 

22-22 

1778 

29 

—  1-67  | 

—  i'33 

—13 

-25 

20 

71 

21*67 

17-33 

28 

—  2-22 

-  .78 

—14 

-25-55 

-2044 

70 

21*1 1 

16-89 

27 

-  2-78 

—  2-22 

-  >5 

—26-11 

-20-89 

69 

20-55 

16-44 

26 

-  3  33 

—  2-67 

-16 

-2667 

-2133 

68 

20 

16 

25 

3-89 

3-ii 

-17 

— 27-22 

-  21-78 

67 

19-44 

I5-56 

24 

-  4-44 

-  3-56 

-  18 

-  27  78 

22  22 

66 

18-89 

15-11 

23 

_  5 

-  4 

-19 

-28-33 

—  2-2-67 

65 

18-33 

1467 

22 

^  5-55 

—  4'44 

—20 

-28-89 

23-II 

64 

1778 

1422 

21 

—  611 

-  4-89 

—  21 

29-44 

-2356 

63 

17-22 

1378 

20 

-  6  67 

—  5-33 

—22 

—30 

24 

62 

16-67 

1333 

19 

—  7-22 

-  5-78 

—23 

-30-55 

—24-44 

61 

161 1 

1289 

18 

-  7-78 

—  622 

—24 

-3III 

-24-89 

60 

15-55 

12-44 

17 

-  8  33 

—  667 

-25 

—31-67 

—2533 

59 

15 

12 

16 

—  8.89 

-  7  II 

—26 

-3222 

-257S 

58 

14-44 

1 1-56 

15 

—  9'44 

-  756 

-27 

-32-78 

—26-22 

57 

13-89 

11*11 

14 

10 

-  8 

-28 

— 3333 

--26-67 

56 

1333 

1067 

13 

—  io-55 

-  8-44 

-29 

-3389 

—271 1 

55 

.2-78 

1022 

12 

—  ii-ii 

-  8  89 

-30 

—34  44 

—27-56 

54 

12*22 

9-78 

11 

— 11-67 

--  9-33 

-31 

35 

-28 

53 

1 1-67 

9-33 

10 

—  1222 

-  978 

-32 

—35-55 

—  28-44 

52 

1 11  I 

8-89 

9 

—1278 

— 1022 

— 33 

—36-11 

-2889 

51 

IQ'55 

8-44 

8 

—i3'3 

—  IO-67 

-34 

—36-67 

—2933 

50 

10 

8 

7 

-13-89 

—  I  I  II 

—35 

37-22 

—29-78 

49 

9-44 

7-56 

6 

—14-44 

—  U56 

-36 

37-78 

—  3022 

48 

8-89 

711 

5 

15 

—12 

37 

38-33 

-38-89 

-3067 

47 

8-33 

6-67 

4 

-15-55 

—12-44 

-38 

\-3Vll 

46 

1  7-78 

6-22 

3 

—  1 6*  1 1 

-12-89 

39 

—39-44 

-3'-56 

45 

7-22 

5-78 

2 

—  1667 

—  13-33 

40 

40 

-32 

44 

6-67 

5*33 

557 


APPENDIX. 


Table  of  commercial  shutters,  showing  the  speed  of  each. 
Where  the  speed  is  distinguished  by  an  asterisk,  it  has  been 
experimentally  determined  by  some  observer ;  in  all  other 
cases  the  speed  is  that  stated  by  the  makers ;  where  no 
speed  is  given,  this  depends  upon  particular  circumstances, 
such  as,  with  the  drop  shutter,  the  use  of  indiarubber  bands, 
etc. 


Class  and  Name. 

Speed. 

Remarks. 

Lowest. 

Highest. 

I. — Exposing  Shutters. 

Lancaster's  Pneumatic  ... 

Newman's  Studio  

Taylor's  Exposing  Flap  ... 
Thornton-Pickard  Studio 

TxtIht  <;  ^\#=m  f.Pnrfr'n  l  f 

Time 
Time* 
Time 

n 
>» 

ws  sec«* 
t75  sec.  * 

£-5   sec   sky,  2^ 
sec.  foreground. 

II. — Rapid  Shutters. 

a  i.  Drop. 

„        „       with  india- 

f  sec. 

j4^  sec. 
TV  sec* 

a  2.  Flap  and  Drop. 

Reynolds  and  Branson's 
"Leeds"   

Reynolds  and  .  Branson's 
"Phcenix"   

a  3.  Double  Drop. 

1- 

ih  sec*| 

TV  sec* 

«V   sec.  sky,  -g\ 
sec.  foreground; 
and  y1^  sec.  fore 
ground,  T^  sec. 
sky. 

Less  for  sky, 
sec* 

Tylar's  Foreground   

Vevers'  Window  Blind  ... 

Time 

?? 

aV  sec* 
-At  sec* 
-jy  sec* 

2V  sec.  sky,  ^ 
sec.  foreground. 

A   sec.  sky, 
sec  foreground. 

■h  sec.  sky,  ft 
sec.  foreground. 

558 


II.  TABLES. 


Class  and  Name. 


a  4.  Rotating  Screens. 

Cadett's  Lightning   

Lancaster's  Instantograph 


Leisk's  Sky   

Underwood's  XL. 


a  5.  Flap  and  Double  Flap. 

Furnell's   

Guerry   

Tylar's  Norden  Flap   


a  6.  Go  and  Return. 

Lancaster's  Chronolux  

Mitchell's  Pneumatic  Re- 
turn   

Pcrken's  Plunge   


Sl'EED. 


Lowest. 


Highest. 


Remarks. 


it  sec-* 
tV  sec-* 

sec* 
X  sec* 


A  sec* 
-.h  sec/ 


Screen  shaped  to 
give  less  sky 
exposure. 

Less  for  sky. 

And  time. 


1T  sec*  j  Sky  ^  sec,  fore- 
ground I  sec. ; 
sky  sec,  fore- 
ground sec. 


a  7.  Blind. 


4  sec* 


i  s  sec' 
sec* 


Kershaw   

Thornton-Pickard's  Time 

.»             it  In- 
stantaneous   

Underwood's  Instantolux 

a  8.  Opening  from  Centre. 
Gotz  Wing  

Lancaster's  '90  Chronolux 
Thornton-Pickard's  Double 

Blind   

Sands  and  Hunter's  Ribbon 

The  "  Stanley  "  

Stereoscopic  Company's... 
Watson's  Double  Snap  ... 

a  9.  Ever-Set. 
L'Atitomatique  


Less  for  sky. 


iU  sec* 

Time*  sec*    :  Sec  table  below. 


..V  sec* 

J.  sec* 

&  sec* 

sec* 

A  sec* 

With  two 

bands,  ^ 

3  sec.  * 

A  sec* 

TffTT  sec. 

17  sec* 

A  'sec* 

•A  scc-* 

sec* 

... 

559 


APPENDIX. 


Speed. 

Class  and  Name. 

Remarks. 

Lowest. 

Highest.) 

■fe  sec* 

„     „  Oval 

-V  sec* 

TV  sec* 

II.  b. — Behind  Lens. 

... 

Sec  table  below. 

II.  c. — Between  Lenses. 

i.  Go  and  Return. 

sec* 

I  sec* 

X  sec* 

Varies  consider- 

ably.* 

Time 

nj  sec* 

2.  Blind  or  Drop. 

Thorn  ton-Pickard's  Blind 

</u  sec* 

See  table  below. 

3.  Centre  \Jpcning. 

4.  Eyelid. 

1  sec. 

too  sec. 

Caldwell's  (Wray)    ... 

A  sec* 

vfa  sec. 

5.  Diamond. 

Sands  and  Hunter's  Patent 

* 

TT8"  SeC- 

Wollaston's  Diaphragmatic 

sec* 

6.  Strip. 

See  table  below. 

7.  Iris. 

Tiy  sec. 

oV  sec* 

Voigtlander's  (Marion)  ... 

J-  sec* 

8.  Rotating  Screen. 

Celeritas  (Adams  and  Co.) 

*h  sec 

Stated    also  to 

work     up  to 

ittVtt  sec. 

II.  d. — In  Front  of  Plate. 

Loman's  Light  Economic... 

\  sec* 

rA  0  sec* 

With  1 -in.  aper- 

ture on  i-plate. 

560 

II.  TABLES. 


Messrs.  Thornton-Pickard  give  the  following  table  for  their 
shutters: —  . 


Size  of 
Shutter. 

No.  of  Turns 

of  the 
Speed  Knob. 

i  Speed  in 
Fractions 

of  a 
Second. 

Size  of 
Shutter. 

No.  of  Turns 

of  the 
Speed  Knob. 

Speed  in 
Fractions 

of  a 
Second. 

" { 

o 
5 

15 

-i 
Tt 

4i 

T)V 

'  ] 

3  in.  ...j 

O 

5 
i5 

tV 

A 

2  in.      ...  j 

5 
'5 

«v 

3i  in.  ...| 

0 
5 
15 

rV 
1 

n 

2}  in.  audi 
2\  in.  { 

0 

5 

!5 

A 
ih 
7V 

*  i 

0 
5 

15 

1 

I 

These  approximate  speeds  have  been  arrived  at  after  a  series  of  very 
careful  tests  with  apparatus  constructed  specially  for  the  purpose.  The 
method  used  gives  undeniably  accurate  results.  The  speed  used  in  this 
table  apply  to  the  "time  and  instantaneous"  shutter,  "instantaneous" 
shutter,  "foreground"  shutter.  The  "extra-time"  shutter  (double-blind) 
pattern  works  at  one  and  a-half  times  these  speeds.  The  "special" 
instantaneous  (double-blind)  pattern  works  at  twice  these  speeds. 

French  Fluid  Measures. 

The  cubic  centimetre,  usually  represented  by  "c.cm.,"  is  the  unit  of 
the  French  measurement  for  liquids.  It  contains  nearly  seventeen 
minims  of  water ;  in  reality,  it  contains  l6-896  minims.  The  weight 
of  this  quantity  of  water  is  one  gramme  :— 

1  cubic  centimetre  =     17  minims  (as  near  as  possible). 


2 

cubic  centimetres  = 

34  - 

3 

5i  . 

4 

68  , 

or 

i  drachm  8  minims. 

5 

85 

>> 

1      n  25 

»» 

6 

102  ,, 

j> 

1      „  42 

»» 

7 

119  - 

H 

1  n  59 

2  drachms  16 

8 

136  „ 

j> 

» 

9 

153  - 

>> 

2      „  33 

10 

170  , 

2      ;,  50 

» 

20 

340  • 

5      n  40 

30 

510  .. 

>> 

1  ounce     0  drachm   30  minims. 

40 

680  ,, 

>> 

1      »  3 

drachms  20  „ 

50 

850  ,, 

1      „  6 

10  „ 

60 

1020 

j? 

2  ounces  1 

0  „ 

70 

iroo 

2  3 

50  •• 

80 

1360     , , 

2     „  6 

40 

90 

1530 

3  1 

30  „ 

TOO 

T700 

3  4 

20 

561  00 


APPENDIX. 


The  Conversion  of  French  into  English  Weights. 

Although  a  gramme  is  equal  to  15-4346  grains,  the  decimal  is  one 
which  can  never  be  used  by  photographers;  hence  in  the  following 
table  it  is  assumed  to  be  1 5^-  grains,  which  is  the  nearest  approach 
that  can  be  made  to  practical  accuracy  : — 


I 

gramme 

I5l 

grains. 

2 

grammes 

— 

30* 

3 

= 

4 

_ 

6if 

or 

I 

drachm 

if 

grain. 

5 



77 

17 

grains 

6 



92i 

I 

32T 

7 

— 

io7f 

1 

47t 

8 

— 

I23t 

2 

drachms 

9 

_ 

I38f 

2 

i8f 

10 



154 

2 

1 1 

_ 

1694 

2 

49t 

12 

184+ 

4t 

13 

— 

2°°5 

20| 

— 

2I5t 

3 

35t 

1  c 

j 

_ 

2^1 

■2 
0 

CI 

J 

16 

= 

2461 

4 

17 

261* 

4 

II 

2ii 

18 

277l 

4 

>» 

37i 

»> 

19 

2925. 

4 

»> 

sn 

>> 

20 

308 

5 

n 

8 

u 

30 

462 

7 

w 

42 

» 

,4° 

616 

10 

16 

»» 

5o 

770 

12 

n 

5o 

tt 

60 

924 

15 

24 

11 

70 

1078 

17 

»» 

58 

i» 

80 

1232 

20 

11 

32 

90 

1386 

23 

11 

6 

11 

100 

1540 

25 

n 

40 

>» 

Conversion  of  Minims,  Drachms,  Ounces,  and  Pints  to  Cubic 
Centimetres  and  Litres. 


Minims  to  c.cm. 

Drachms  to  c.cm. 

Ounces  to  c.cm. 

Pints  to  Litres. 

OO5916 

3'5495 

28-396 

0-56792 

2 

0-11832 

7-0990 

56-792 

IT3584 

3 

0-17748 

106485 

85-188 

1-70376 

4 

0-23664 

14-1980 

II3-584 

2-27168 

5 

0-29580 

17-7475 

141-980 

2-83960 

6 

0-35496 

21-2970 

170-376 

3-4Q752 

7 

0-41412 

24*8465 

198-772 

3'97544 

8 

0-47328 

28-3960 

227*168 

4-54336 

9 

o'53244 

31-9455 

255*564 

5-11128 

562 


II.  TABLES. 


Conversion  of  Grains  and  Ounces  into  Grammes. 


Grains  to  Grammes. 

Ounces  to  Grammes. 

Grains  to  the  Ounce- 
Grammes  to  icoc.cm. 

1 

0*06479 

28*3495 

O  22817 

2 

0*12958 

56  9660 

045635 

3 

0-19437 

850485 

06845  2 

A 

4 

0*259 16 

1 1 2*^080 

A'AT  0  f~in 

u  y 1 zuy 

5 

0*32395 

I4I7475 

1*14086 

6 

0*38874 

I7OO97O 

1*36904 

7 

Q'45353 

I984465 

1*59721 

8 

0*51832 

2267960 

1*82538 

9 

0*58311 

255'1455 

2-05356 

Table  showing  the  Correction  for  Actinic  Foci  with 
Monocles  or  Spectacle  Lenses. 

Proportion  between  Image  a?id  Object. 


iV 

A 

ITT 

A 

A 

1% 

'& 

s 

T(T 

±. 

f  IOO 
A/  2 

no 
2*4 

120 

29 

I30 

34 

140 

39 

I50 

4'5 

l6o 
5*1 

170 

58 

l8o 

6*8 

190 

72 

200 
80 

I50 

A/  3 

3*6 

180 
4*3 

195 
5'i 

210 

5  9 

225 
6*8 

24O 

77 

255 
87 

270 
97 

"285" 

io-8 

300 
120 

/  200 
A/  4 

220 

48 

240 

5'8 

260 
6*8 

280 
7'8 

3°o 
90 

320 
10  2 

340 
116 

360 
130 

380 
144 

400 
16  0 

/  250 
A/  5 

275 
61 

300 

IL 

325 

35o 
9*8 

375 
"*3 

400 
128 

425 
145 

45o 
162 

475 
181 

500 
200 

/  300 
A/  6 

330 
7'3 

360 

8*6 

390 

IOI 

420 
117 

450 
135 

480 
154 

5io 
173 

540 
19*4 

57o 
217 

6co 
240 

/  35o 
A/  7 

"385" 
8-5 

420 

IOI 

455 
n*8 

490 
137 

595 
15-8 

560 

179 

595 

20*2 

630 

22*7 

665 
253 

700 
280 

/"  400 
A/  8 

440 
97 

480 
"•5 

520 
13*6 

560 
157 

600 
180 

640 
205 

680 
23I 

720 
25*9 

760 
289 

800 
320 

/  45o 
A/  9 

495 
10*9 

340 
130 

585 
152 

630 
177 

675 
203 

720 

230 

765 
260 

8lO 

29*2 

855 
327 

900 
360 

/  5oo 
A/  IO 

55o 

12*1 

600 
14*4 

650 
16*9 

700 
196 

750 

22*5 

800 

256 

85O 

289 

900 
324 

950 
361 

I, coo 

400 

563 


APPENDIX. 


English  Measures. 

Proportion  between  Image  and  Object. 


A 

A 

A 

1  0 

c 

To" 

A 

8 

1  0 

A 

1 0 

To 

f  3lt 
A/tV 

41 

117 

41 

jl 
8 

5* 

tVo 

5* 

1  3 

Tffo 

51 

3 
TU 

64 

5  1 
2  4  0 

ft* 
2  9 
i^¥ 

7* 

if 

3 

TS 

71 
* 

/  5* 
A/  \ 

3 
2  0 

7i 

4  3 
?40 

71 

5  1 

2~i^) 

8* 

5  9 

"5  4¥ 

75  o 

9s 
77 
34  0 

I°A 

Air 

1  of 

9S? 

9 
"So" 

"if 

4 

f  n 

A/i 

~8f 

1 

ioi 

l  7 

TO" 

II 

1  3 

0  0 

ii! 

3 
8 

12* 

5 1 
■42IT 

I3f 

2  9 

T.TT 

Hi 

u 

15 

3 
% 

15! 

I 

/  9*3 
A/  A 

IO| 

4" 

TIT 

it 

13! 

4  9 

l^-o" 

l*ir 

38 
11 

i6f 

II 

17! 

SI 
TUO- 

18! 

1  S  1 

2  4U 

19** 

I 

/"it 

A/i 

13 

14* 

43 

T2  "0" 

i5l 

10  1 

2  4TT 

» 

i7! 

tt 

iA 

20^ 

173 

-2--4-0 

21* 

97 

tto 

22A 

23I 

/  I3tt 

A/,ir, 

ISA 

1  7 

4  4 

1DT<7 
10  1 

240 

i7t§ 
1 

I9t. 

20H 

T¥XT 

22A 

17  9 
24  0 

23  A 

101 

T5T7 

24! 

2  3  7 
24  0 

26ft 

2 

27A 
1  o 

/  i5! 

A/  i 

I7A 

I9H 

ttt 

IX 
3  0 

22 

23l 

I 

25A 

4  I 

TS 

26| 

If 

17 

8  0 

30 

1 A 

3>2 

ii 

/  17! 
A/§ 

10  0 
241T 

2 

23  A 

3TT 

2411 

3 
4 

26| 

6 

291 

2  3 
"24 

3°8 

iA 

3^ 

33A 
if 

354 
1* 

/  19! 
A/  i5. 

21  T.T 

1 

3. 

251 
1  7 

f"4 

27^ 

5 

29§ 

1  5 

TB" 

311 
I  tS 

334 
1* 

351 
1 A 

37  A 

39A 
1 

In  the  above  tables  f  =  the  solar  focus. 

A  f— the  correction  for  actinic  rays. 


Preparing  Percentage  Solutions. 

[Anthony  s  Annual.) 
By  C.  C.  Sherrard,  Ph.  C. 

The  first  table  gives  percentage  solutions ;  the  second  gives  parts 
in  1,000  or  less.  The  use  of  the  first  is  as  follows  :  Run  down  column 
one  until  the  correct  percentage  wanted  is  found,  then  move  to  the 
right  along  the  line  until  the  column  is  found  giving  the  amount  of 
fluid  measure  to  be  made  up ;  at  the  intersection  will  be  found  the 
weight  of  salt  required.  It  must  be  remembered  that  this  is  the 
amount  of  water  to  take,  and  not  q.s.  water  to  make  the  volume  ; 
also  that  these  tables  are  true  only  for  water,  and  not  for  alcohol  or 
othcr  fluids. 


564 


».  TABLES. 


For  Making  any  Quantity  of  Percentage  Solutions. 


1  fluid 
water 
ne  salt 

i  fluid 
water 
le  salt 

3  fluid 
water 
le  salt 

♦  fluid 
water 
le  salt 

5  fluid 
water 
le  salt 

0  fluid 
'  water 
le  salt 

6  fluid 
water 
le  salt 

For  each 
ounce  of 
take  of  tl 

For  each  : 
ounces  ot 
take  of  tl 

For  each 
ounces  ot 
take  of  tl 

For  each  . 
ounces  ot 
take  of  tl 

For  each 
ounces  of 
take  of  tl 

For  each  1 
ounces  of 
take  of  tl 

!  For  each  j 
ounces  of 
take  of  tl 

To  make 

Grains. 

Grains. 

T,  rains. 

Grains. 

Grains. 

Grains. 

.  Grains. 

1  per  cent 

2  per  cent 

3  per  cent 

4  per  cent 

5  per  cent 
io  per  cent 
IS  per  cent 
20  per  cent 
25  per  cent 
40  per  cent 

4*557 
9-114 
13-671 
18-228 
22-785 
45*57 
68-355 
91-14 
113-925 
182-28 

9-114 
18-228 
27-352 
36*456 
45*57 
91-14 
136-71. 
182-28 
227-85 
364*56 

13-671 
27*342 
41*013 
54-684 
68-355 
136-71 
205*065 
273*42 
341*775 
546*84 

18-228 
36*456 
54*684 
72*912 
91*14 
182-28 
273*42 
364*56 
455'7o 
729*12 

22-785 
45'57o 
6d*355 
91-14 
113-925 
227-85 
341-775 
455-7o 
569-625 
9x1*4 

45*57 
91-14 
136-71 
182-28 
227-85 
455-7 
68-355 
911-4 
•i39-25 
1822-8 

72-912 
145*824 
218-416 
291-648 
364-56 
729- 1 2 
109368 
1458-24 
1822  8o 
2916-48 

For  Making  any  Quantity  of  Solution  when  stated  in  Parts 
per  1,003,  100,  etc. 


■ 

For  each  1  fluid 
ounce  of  water 
take  of  the  salt 

For  each  2  fluid 
ounces  of  water 
take  of  the  salt 

For  each  3  fluid 
ounces  of  water 
take  of  the  salt 

For  each  4  fluid 
ounces  of  water 
take  of  the  salt 

For  each  5  fluid 
ounces  of  water 
take  of  the  salt 

For  each  10  fluid 
ounces  of  water 
take  of  the  salt 

For  each  16  fluid 
ounces  of  water 
take  of  the  salt  i 

To  make 
solution  of 

Grains. 

Grains. 

Grains. 

Grains. 

Grains. 

Grains. 

Grains. 

1  in  1,000 
1  in  500 
1  in  400 
1  in  300 
1  in  200 
i  in  100 
1  in  50 
1  in  25 
1  in  10 
1  in  5 

•4557 
•9114 
1-139 

1*519 
2*2785 
4*5£7 
9*114 
18*228 
45*570 
91*14 

•9114 
1-8228 
2*278 
3*035 
4*557 
9-114 
18*228 
36-456 
91*140 
182-28 

1*3671 
2*7342 
3*4»77 
4*557 
6-8355 
13*671 
27-342 
54*684 
136*710 
273'42 

1-8228 
3*6456 
4*557 
6*076 
9*114 
18-228 
36-456 
72*912 
182*280 
364-56 

2  278 
4*557 
5-695 
7*59 
u*39 
22-785 
45  57 
91*14 
227-85 
455*7 

4*557 
9*114 
11*392 
15*19 
22*785 
45*57 
91*14 
182*28 
455-70 
yii'4 

7-291 
14-582 
18*228 
24304 
36-456 
72*912 
145824 
2yi*648 
7 29- 120 
■458*24 

We  may  say  that,  in  giving  the  above  figures,  the  resulting  solution 
is  correct  as  regards  percentage  composition,  though  it  may  measure 
slightly  more  than  the  water  taken,  owing  to  the  increase  in  volume 
which  always  takes  place  in  some  degree  when  a  solid  passes  into  a 
solution  in  a  given  amount  of  liquid.  This  expansion  is  not  appreciable 
for  small  amounts  of  the  solid,  say  up  to  5  per  cent.,  but  .it  25  per 
cent,  or  more,  it  may  be  noticeable. 

565 


APPENDIX. 


Relative  Exposures  for  Varying  Proportions  of  Image  to  the 
Original. 

By  W.  E.  Debenham. 


Proportion  of 
image  to  original 
(linear). 

Distance  of 
image  from  lens 

Proportionate 

Exposures 
proportioned  to 

in  terms  of 

exposures.* 

that  required  for 

principal  focus. 

copying  same  size. 

i 

so" 

T  1 

1  30 

I -07 

•27 

1 

,  1 

IIO 

•28 

lTF 

1  lV 

I  "21 

'3 

H 

1-27 

jl 

I 
6 

136 

'34 

l 
4 

I -56 

'39 

.1 

I* 

2-25 

•56 

I 

If 

3-06 

76 

I 

2 

4 

I 

(same  size) 

2 

3 

9 

2 '25 

3 

4 

16 

4 

4 

5 

25 

6-25 

5 

6 

36 

9 

6 

7 

49 

12-25 

7 

8 

64 

16 

8 

9 

81 

20*25 

9 

10 

100 

25 

IO 

1 1 

121 

30-25 

1 1 

12 

144 

36 

12 

13 

169 

42-25 

13 

H 

I96 

49 

14 

15 

225 

56-25 

15 

16 

256 

64 

16 

17 

289 

72-25 

17 

18 

324 

81 

18 

19 

36i 

90-25 

19 

20 

400 

100 

20 

21 

441 

110-25 

21 

22 

484 

121 

22 

23 

529 

132-25 

23 

24 

576 

144 

24 

25 

625 

156*25 

25 

26 

676 

169 

26 

27 

729 

182-25 

27 

28 

784 

196 

28 

29 

841 

210-25 

29 

30 

900 

225 

30 

3i 

1 

961 

240-25 

566 


II.  TABLES. 


Table  of  Enlargement  or  Reduction. 


Focus 

c 

o 

Enlarge- 
ment. 

of  Lens 
in 

ts 

3 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

Inches 

73 

Inches 

Inches 

Inches 

Inches 

Inches 
es. 

Inche 
DC  ies. 

Inches 

Inches 



2 

J 

A 
i\ 

4 

8  ' 

1 0 

1 2 

16 

l8 

g 

1 
V 

15 

4 

3 

2i 

2  a 

-72 

-71 

A 

2h 

/■ 
/ 

A 
/V 

5 

7l 

IO 

1Z2 

J5 

17$ 

20 

22* 

g 

i 
I 

13 

3? 

1  I 

31 

it 

3 

->1  1 

*rs 

27 

2ld 

A 
/\ 

3 

r 
J 

A 
/\ 

9 

12 

1  c 
lD 

iX 

2 1 

-7  yf 
24 

27 

g 

g 

6 

/l1 

4$ 

4 

3f 

3a 

3? 

31 

A 

3J 

( 

A 

7 

1 0 

H 

4| 

I  7  1 

'  ? 

2 1 

-7/1  > 
242 

9X 

3 1 1 

3*3 

g 

1 

li 

? 

7 

5 

4i 

4s 

4 

•3  1  5 

3ro 

A 

4 

J 

1  /v 

y 
o 

1 2 

1  a 
1 0 

20 

24 

oX 

32 

3° 

4a 

g 

1 

V 

B 

5 

r  1 

5? 

c 

A  * 

4.-, 

4f 

4r 

A 

f 

A 

9 

*32 

iX 

I  0 

0^  1 

27 

7 1 1 

0X2 

3° 

4°  2 

g 

1 

g 

9 

f. 
0 

C  •? 

5s 

rl 
5t 

57 

r  1 

5ic 

A 

5 

t 
\ 

A 

I  o 

20 

2C 

3° 

7  r 

35 

40 

45 

D 

g 

I  o 

71 
161 

°f 

0 1 

0 

5£ 

r  1 

5r 

5ff 

A 

i 

A 

1 I 

33 

3°  2 

44 

49  2 

13 

K. 

g 

Xi 
«* 

7  8 

6""' 

fi2 

fi  •'5, 

A 

6 

{ 

A 

2 

iX 

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APPENDIX. 


o  ^  ™ 


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cjCoOrtCoOS  OO  g  op 

U<C/3P*U<C/3Ph<  (/}  PL,  <  73  P- 

570 


II.  TABLES. 


Table  of  Solubilities  of  Various  Chemicals. 

alcohol-ether  —  equal  parts  ol  alcohol  and  ether, 
dec.  =b  decomposed, 
m.  ~  miscible  in  all  proportions, 
s.  —  soluble, 
s.  s.  =  slightly  soluble, 
v.  s.  =  very  soluble, 
nsol.  —  insoluble.  1 


u 

bp 

u 

j    o  :  > 

ilin 
ve. 

u 

•~  J* 

1 
A 

3  r/ 
0  Ho 

gl 

ts  0 
isso 

5  if 

• 

>  parts  c 
vater  di 

100  par 
Icohol  d 

10  parts 
disso 

Remarks. 

0 

n 

Acetone  



m. 

m. 

m. 

m. 

Acid,  Acetic  

m. 

m. 

m. 

,,  Boracic   

4 

29 

25  boiling 

,,  Carbolic   

,,  Citric  

140 

200 

,,  Formic   

s. 

s. 

DI. 

„  Gallic  

1 

33 

I2"5 

,,     Hydrobromic  ... 

dec. 

dec. 

,,    Hydrochloric  ... 

m. 

m. 

,,     Hydrofluoric  ... 

m. 

m. 

,.  Lactic  

m. 

m. 

m. 

m. 

,,  Nitric  

m. 

m. 

dec. 

dec. 

,,  Picric   

s.  s. 

5 

s. 

s. 

,,  Pyrogallic  

5° 

100 

90 

V.  s. 

,,  Salicylic   

023 

8 

dec. 

28-57 

,,  Sulphuric  

m. 

m. 

dec. 

,,  Sulphurous 

s. 

dec. 

s. 

,,  Tannic  

•8 

'5 

120 

,,  Tartaric   

25 

100 

20 

Alum  (ammonia) 

„  (potash)   

13 

358 

insol. 

insol. 

,,  (chrome)   

9"5 

50 

insol. 

insol. 

Amidol   

42 

Ammonium  Bichromate 

9 

422 

s.  s. 

,,  Bromide 

v.  s. 

o'n 

o-8  %  in 

,,    Carbonate  ... 

25 

dec. 

s.  s. 

alcohol-ether. 

,,    Chloride  ... 

30 

100 

,,  Citrate  

200 

40J 

s. 

,,  Iodide   

165 

V.  s. 

25 

05 

5%  in 
alcohol-ether. 

Nitrate  

200 

43  cold,  80 
boiling 

„  Oxalate 

33 

50 

s. 

,,  Sulphocyanide 

160 

V.  s. 

v.  s. 

,,  Sulphite 

100 

dec. 

s.  s. 

s.  s. 

Amyl  Acetate   

insol. 

insol. 

m. 

m. 

Aniline   

3 

V.  s. 

v.  s. 

Barium  Bromide  

100 

168 

s. 

V.  s.  in  benzine. 

57' 


APPENDIX. 

Table  of  Solubilities  of  Various  Chemicals  {Continued), 


Barium  Chloride  

,,  Iodide   

,,  Nitrate   

,,  Hydroxide 
(baryta) 

Benzine  

Borax   

Bromine  

Cadmium  Bromide 

„     &  Amm.  Brom 

,,  Chloride... 

,,     Iodide  ... 

Calcium  Bromide 
,,  Chloride 


,,  Carbonate 

Hydrate 
,,  Iodide 

Cobalt  Bromide 
„  Chloride 
,,  Iodide 
„  Nitrate 
,,  Sulphate 

Copper  Bromide 
,,  Chloride 
,,  Nitrate 
,,  Sulphate 

Cyan  in   

Dextrine  


Eo*in   

Erythrosin   

Eikonogen   

Ether  Acetic  

,,    Sulphuric  ... 

Glycerine   

Glycin   

Gold  Chloride 

Hydroquinone  ... 

Hydroxylamine  Hydro- 
chloride   

Iodine   

Iridium  Chloride 

Iron  Chloride  (ferric) 


2  °  C 

O  T> 


36 
200 


4*7 
insol. 
6 


•06 


130 
400 


100 
400 

insol. 


100 

33 
40 


42 
9 

8 


100 
5' 


[60 


o  ? 


3co 
35 


insol. 
200 
dec. 
v.  s. 

v.  s. 

650 

i35 

166 
650 

insol. 

135 
i33 


0'26 


dec. 
dec. 
m. 


0  o 

§1 

"c3 


133 
10  at  300  c. 


v.  s. 
s.  s. 


o-i  cold, 
5.5  boiling 

insol. 

•9  boiling 


13  cold,  70 
boiling 
102 


13  cold,  70 
boiling 
insol. 
insol. 
v.  s. 


sol. 


s.  s. 
s. 
s. 
insol. 
sol. 


s. 
insol. 
m. 


m. 
insol. 

c'4 
0-4 


insol. 
insol. 


insol. 

insol. 

m. 
s.  s. 


Remark-' 


10  %  in 
glycerine. 


jl-eiher. 


6'2 

alcohol 

4%  in 
alcohol-ether. 


50%  in 
alcohol-ether. 


insol.  in  abso- 
lute, s.  s.  in 
dilute  alcohol. 


s.  in  glycerine. 


II.  TABLES. 

Table  of  Solubilities  of  Various  Chemicals  {Continued), 


Iron  Chloride  (ferrous) 
,,        ,,  Iodide 
,,        ,,   Oxalate  (ic) 
„  (ous) 

.,  Sulphate   

.,  Nitrate  

.,  Ammonio-citrate 
,,  -oxalate 
..    Sodio  ,, 
,,   Ammonio  Sulphate 

Bromide   

Lead  Acetate   

,,  Chromate   

,.  Nitrate  

Lithium  Bromide 

.,      Carbonate  ... 
Chloride  ... 

,,  Iodide   

Magnesium  Bromide 
,,  Chloride 

.,         Iodide  ... 
Sulphate 
Mercury  Herchloride 

Metol   

l'aiamidophenol  

Palladium  Chloride  ... 
M  atinum  Bichloride  .. 
Potassium  Acetate  ... 

,,  Aceto-tungstate 
,,    Bicarbonate  ... 

Bichromate  .. 

Bromide  

Carbonate 

,.  Chlorate  

,,  Chloride  

,,  Chloroplatinite 
,,  Chromate 

Citrate   

Cyanide  

„  Ferricyanide... 
,,  Ferrocyanide 
,,    Hydrate  ...  . 

Iodide    ...  . 


2°j3 
o  :  > 

<=°iO<« 
Sic 


140 

V.  s. 
V.  s. 

0-05 

60 
50 
25 
90 


66 
insol. 
50 
143 
0-77 
82 
100 
100 
160 


s. 

I  '2 

S. 
IOO 

J  90 

s. 
33 
12 
50 

149 

6-5 
32 
17 
50 
166 
I  coo 

40 

28 

200 


2? 


dec. 


0*03 


insol. 
140 

290 

0-78 
146 
i33 
i33 
37o 

133 
700 


200 
800 

V.  s. 

50 

94 


305 

50 

57 
V.  s. 

60 
232 
part.  dec. 
776 

50 
400 
200 


2  v> 

8/3 


Remarks. 


insol. 

insol. 
s.  in  dilute 

s. 


insol. 


s.  s. 
s. 


insol. 


12  insol. 
insol.  insol. 
insol. 
v.  s. 
insol. 

s.        ;  s. 

S  ::: 

50  cold,  sco  I 
boiling 

s. 
in&ol. 

33  cold,  93   25  with  hyHro- 


s.  in  an  alkaline 
oxalate. 


boiling 
s. 

4"5 

S. 
V.  s. 
30  cold,  50 
boiling 

s. 
insol. 
dec. 
o"i  5  cold.  7 
boiling 
insol. 
insol. 
s.  s. 
insol. 
insol. 
insol. 

1 '2 
insol. 
insol. 
s.  s. 


chloracid 
5*5 

I.  s. 


insol. 

insol. 
insol. 
dec. 

0"2 

insol. 
insol. 

insol. 
insol. 
insol. 


v.  r.  in  caustic 
alkalies. 


005  %  in 
alcohol-ether 


o-8  %  in 
alcohol-ether. 


573 


APPENDIX. 


Table  of  Solubilities  of  Various  Chemicals  {Continued). 


ioo  parts  of  cold 
water  at  15°  C,  or 
590  F.,  dissolve. 

100  parts  of  boiling 
water  dissolve. 

100  parts  of 
alcohol  dissolve. 

100  parts  of  ether 
,  dissolve. 

Remarks. 

Potassium  Metabisul- 

phite  ... 

33 

v.  s. 

insol. 

insol. 

,,  Nitrate   

3° 

335 

insol.  in 

cold,  2  in 

„  Nitrite   

boiling 

100 

200 

Oxalate   

33 

5° 

•  "1 
insol. 

•  "" 
insol. 

.,  Permanganate 

0  5 

10 

insol. 

,,  Silicate   

33 

IOO 

dec. 

dec. 

Sulphocyanide 

217 

V.  s. 

sol. 

Sulphide  

„    (bi) Tartrate  ... 
Potassium  Tungstate 

o'4 

.  ••• . 
inso  . 

7 

insol. 

S. 

inso  . 

s. 

insol. 

Pyrocatretim   

v.  s. 

V.  s. 

v.  s. 

v.  s. 

s.  in  alcohol- 

Pyrogallol   

.  40 

V.  s. 

V.  s. 

v.  s. 

ether. 

Pyroxylin   

insol. 

in  0  . 

insol. 

insol. 

Resorcin   

86"4 

_ 

s. 

insol. 

Silver  Albuminate  ... 

insol. 

'nsol 

insol. 

insol. 

Acetate   

„  Bromide   

'  1 

.  '*' , 

'  1 

*   "  1 
insol. 

„  Carbonate  

insol 

insol' 

in^ol 

insol. 

,,  Chloride   

insol. 

insol. 

insol! 

insol. 

„  Citrate   

,,  Cyanide   

.  ••• , 

.  "• , 

.  ••• . 

,,    Iodide  ,j   

insol. 

inso  . 

ins.°. 

insol. 

Nitrate   

100 

200 

15  cold,  25 

s. 

boiling 

„  Nitrite   

dec 

insol 

„  Oxalate   

3  0-4 

s. 

insol. 

„  Oxide  

insol. 

insol. 

insol. 

insol. 

,,  Sulphate   

Sodium  Acetate  

92 

204 

45 

insol. 

„  Aceto-Tungstate 

s. 

v.  s. 

s. 

insol. 

,,     Bicarbonate  ... 

10 

dec. 

insol. 

insol. 

Bichromate  ... 

V.  s. 

V.  s. 

dec. 

dec. 

,,  Bisulphite 

v.  s. 

V.  s. 

insol. 

insol. 

,,  Bromide   

85-5 

154 

6 

0-08 

20  %  in 

,,  Carbonate 

93 

445 

insol. 

insol. 

glycerine. 

,,  Chloride  

35 

39 '6 

insol. 

„  Citrate   

28 

204 

45 

insol. 

,,  Hydrate  

60 

127 

s. 

insol. 

,,  Hyposulphite... 

IOO 

V.  s. 

insol. 

insol. 

,,  Iodide   

180 

310 

8-4 

027 

„  Nitrate   

88 

IOO 

3 

,,  Nitrite   

.,  Oxalate   

3*5 

7 

insol. 

insol. 

„  Phosphate 

15 

260 

insol. 

insol. 

,,  Silicate   

40 

s.  s. 

dec. 

dec. 

„  Stannate  

61 

s.  s. 

insol. 

insol. 

574 


II.  TABLES. 


Table  of  Solubilities  of  Various  Chemicals  (Continued). 


V 

B 

o    •  > 

— 

of  c 

s°c 

ssol 

ts  0 

isso 

5  % 

« V 

100  parts  0 
water  di 

100  par 
alcohol  d 

100  parts ( 
dissol 

Remarks. 

Sodium  Sulphate 

5° 

200 

s. 

,,       Sulphite...  ... 

25 

100 

insol. 

insol 

„  Tartrate  

5° 

v.  s. 

insol. 

insol. 

,,       Tungstate  ... 

55 

124 

insol. 

insol. 

Strontium  Bromide  ... 

IOO 

133 

s.  s. 

,,        Chloride  ... 

55 

IOO 

s.  s. 

,,  Iodide 

200 

400 

s.  s. 

,,  Nitrate 

Sulphocarbonide 

9 

v.  s. 

V.  s. 

insol. 

Thiosinamine   

s.  s. 

s. 

s. 

s. 

Uranium  Bromide 

IOO 

200 

s. 

.,       Chloride  ... 

V.  s. 

V.  s. 

v.  s. 

,,  Citrate  

s. 

s. 

insol. 

insol. 

,,  Iodide  

,,  Nitrate 

200 

V.  s. 

33'3 

25 

Zinc  Acetate   

,,  Bromide   

320 

V.  s. 

s'oi. 

sol. 

,,  Chloride   

300 

V.  s. 

V.  s. 

,,  Iodide  

300 

v.  s. 

V.  s. 

.,  Sulphate   

142 

200 

insol. 

Table  Showing  at  a  Glance  the  U.  S.  No.  for  All 
Diaphragms. 


F. 

U.  S.  No. 

1-'. 

U.  S.  No 

1 

4-25  ... 

  112 

\\ 

  -097 

4-5 

  1-26 

1-414  ••• 

475  ••• 

  1-41 

1-5 

  -140 

5 

  156 

175  ••• 

  'I91 

525  ... 

  172 

2 

55 

  1-89 

2-25 

:::  -3i6 

5656  ... 

  20 

2-5 

  -390 

575  ••• 

  206 

2-828  ... 

6 

2*25 

2  75  - 

  -472 

6-25  ... 

  2-44 

3 

  562 

6-5 

  264 

3-25 

  -66o 

675 

  284 

3'5 

  765 

7 

  306 

375 

  -878 

7-25  ... 

  3-28 

4 

  ro 

7*5 

  351 

575 


APPENDIX. 


F. 

U.  S.  No. 

F. 

I  ... 

"2*7  C 
J  10 

45 

d'O 

...                 ...         -J.  V 

8-2; 

/l  •'T'C 

!  4^ 

8-5 

A-cr 

/17 
H-l 

875 

40 

9 

5  -06 

AO 

...  3 

CO 

7  .1         • •  • 

...                ...         j  U4 

r  t 
j  * 

y  1  J         •  •  • 

IO 

6-2; 

JJ 

II 

T  c6 

C  A 

1 1  I 

1  1  j1  ••• 

r  r 
3  3 

12 

  9° 

50 

...          ...      ■it-'  j"*-" 

57 

IA 

12*25 

5° 

I  C 

j  ... 

14-06 

16 

i6*o 

60 

17 

18-06 

61 

18 

20*25 

62 

IO 
1  J 

22*56 

u3 

20 

6a 

21 

z/  3"-" 

6; 

22 

•  •  •           ...      J^  J 

66 

22-62 

32'0 

67 

J 

"2  ^-06 
JJ  ^ 

68 

24 

36*0 

6o 

j           •  • « 

70 

26 

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28 

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73 

20 

y            . .  .• 

C2'C6 
j  j 

7A 

J              « •  • 

c6*9  C 

7  C 

2  I 

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76 

^2 

f\AT\ 

...         ...  "4 

77 
78 

JJ            •  •  • 

68-o6 

34 

72'2C 

...          ...      /  ^  ^  j 

7Q 

03  ... 

76'c;6 

...      /  *-"  0" 

80 

36 

80-0 

8l 

37 

0  j  3W 

82 

38 

00*2  C 

8^ 

39 

q*;-o6 

84 

40 

ioo-o 

85 

4i 

 105-06 

86 

42 

 110-25 

87 

43 

115-56 

88 

44 

 1 2  TO 

89 

U.  S.  No. 
...  126*56 
...  128-0 
...  132-25 
...  138-06 
...  144-0 
,..  150-06 
...  156-25 
..  162-56 
..  169*0 

..  I75-56 
182*25 
..  189-06 
..  196-0 
..  203-06 
..  210-25 
..  217-56 
..  225-0 
..  232*56 
..  240-25 
..  248-06 
..  256-0 

264*06 
..  272*25 
..  280-06 
..  289*0 
..  297*56 
..  306-25 
..  315*06 

324'o 
..  333-o6 
..  342-25 
..  351-56 
..  301.0 
..  37o-56 
..  380*25 
,.  390  06 
..  400-0 
,.  410*06 
..  420-25 
..  430  56 

440'0 
,.'  45I-56 
,.  462*25 
.  473-06 

484-00 
'.  495*o6 


576 


II.  TABLES. 


90 

9050 

91 

92 

93 
94 


U.  S.  No. 

...  506-5 

...  5120 

...  517-56 

...  5290 

...  54056 

...  552-25 


95 
96 

97 
98 

99 
100 


U.  S.  No. 

.  564-06 

.  576-0 

.  58806 

.  COj'2  5 

.  612  56 

.  625-0 


Inverse  values  of    and  of 
n 


(lOQ1^)  (US6C* in  Pnotometrv)- 


n 

x 

n 

(— —  V 

n 

1 
n 

/     n  y 

n 

1 
n 

/  \ 

V  IOO — n/ 

\  I  '  »  —11/ 

\  100 — 1 / 

I 

I* 

34 

0294 

•245 

67 

0149 

4-08 

2 

•5 

35 

•0286 

•289 

68 

0147 

451 

3 

•333 

36 

0278 

■316 

69 

■0145 

495 

4 

•25 

37 

•0270 

•344 

70 

•0143 

5'44 

5 

•20 

38 

0263 

•377 

7i 

0141 

609 

6 

•167 

39 

0256 

•408 

72 

•0139 

6- 60 

7 

•143 

40 

•0250  • 

■445 

73 

0137 

7-29 

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74 

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8- 10 

9 

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42 

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10 

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43 

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76 

0132 

1002 

11 

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77 

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12 

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0222 

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78 

•0128 

1257 

13 

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79 

0127 

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14 

•0714 

47 

0213 

■7S7 

80 

•0125 

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48 

0208 

•852 

81 

0123 

181 

16 

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4y 

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82 

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20-8 

17 

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•0419 

50 

020 

r 

83 

•0120 

23-8 

18 

0556 

•0482 

51 

0196 

108 

84 

•01 19 

27-4 

19 

•0526 

•0550 

52 

0192 

116 

85 

0118 

321 

20 

'°5  ^ 

•0625 

53 

•0189 

127 

86 

01 16 

365 

21 

•0476 

•0706 

54 

•0185 

136 

87 

01 15 

44'7 

22 

•0454 

•0795 

55 

0182 

1 -48 

88 

01 14 

23 

•0435 

•0892 

56 

0179 

163 

89 

01 12 

24 

•0417 

•0992 

57 

■OI75 

176 

90 

01 1 1 

25 

•040 

III 

58 

•0172 

rc,o 

91 

01 10 

26 

0385 

•123 

59 

•0169 

207 

92 

0109 

27 

•0370 

•137 

60 

0167 

225 

93 

•0108 

28 

•0357 

•151 

61 

0164 

241 

94 

•0106 

29 

•0345 

166 

62 

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2-66 

95 

0105 

30 

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183 

63 

•0159 

298 

96 

0104 

3i 

0323 

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64 

•0156 

3'i5 

97 

0103 

32 

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65 

•OI54 

3-46 

98 

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33 

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•242 

66 

0151 

376 

99 

OIOI 

577 


p  p 


APPENDIX. 


uiiu'ssbioj 


uinipos 


uiniuouiuiv 


mmss^oj 


umipog 


•bjuoxxiuiv 


S2 

S  N 


•apiuiojg 
uint'ss-B^oj 


•apiuiojg 
raniuouiuiv 


•So 


<D  o 


Q         3  g 


.'is 

0)W 


Oh  CD 

tfl  (A 

'"els 

C  rt  rt 


II  k, 

i..  oJXil-i>l>nio3 

CQUUJQQWW 


73  "U         d  tfl 

-.2.2  = 

WW    WW  W 


3  u 

H  c 


So 


o  >, 
WW 


;7« 


II.  TABLES. 


M  % 

in  m  b  00 


'O  ^ 


o      .  o 


b  b  £  o     000"     0  o 

£  g 
<  o 


p 

0  O 

V 
u 

0) 

O  0 

r>»             ui    ;    ;    ; 10 

0 

!£?  9, 

10  -J- 
b  b  g 
:     **  :  :  o  o  >o 

O 

11S      0      mo^o  u-ico  « 

N,       ;p\:tmflNOH     ;     ;     ;  ; 

0       •  M   N     •     -     •  £  M 
O 

c 

OQ 

0  ' 

b  m 

b   '  "  **  **  m 
0 

b  b 

0  0    '  r'    '  0  '«  «  m  V.  "0 
0 

b 

mo  0  + 

«       00  JLO  M 

0  0 

0 

g  10      00  00        PI   0\  mJ  PI 

pi    pi  pi      *pi  M  n  «  M 

PI  N  P) 

-       '    '    °  m  pi  ' 
O 

N    B    '«    tl    O    '»     N    '»    H    M    '«    H    N     fl  KM 

0 

Wi 

N 

::::::  i:  :  :6 

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ai2c  nn«    ^^^^  ~         -  _  Cu 

-    trt::::iooo     o  o  (/)  iu::  .2 


579 


APPENDIX. 


.5    £  n 


^  *  R 


9 


CO  u 

Hi 


a  © « 

«8a 


00  o 


-a  td 

o  o 


Hill 

Sortie 
cd  cS  .C  o 


T3 

o 

(A 

-a  <u 
'7)  5 


O  3 

.a  cr 

cd  oj 

.a  W 


—  * 

"o'tB 

o  b 


So 

OJ  ft 


o 

ON 

00 

cd 

cd 

So 

«] 
J) 

O  c 

s  o 

cd 

,„  w  rn  O  tn  O  ih  o 

s.fS  l-e  ^-s  §  -e 

!>.        <i         M  O 


&  3  £ 


rt  o 


580 


rt  .2  g  ts  5  -2 .2  o 

.2  .2  -£  <u  2  .2  rt 
00  cd  13 13  0  o  .J y 


n. 
2 

3 
4 
5 
6 

7 

8 

9 

10 

ii 

12 

13 
14 
iS 
16 

17 
18 

19 

20 

21 

22 

23 

24 

25 
26 

27 

28 

29 
30 

31 

32 

33 
34 

36 
37 
38 
39 
40 


II..  TABLES. 


of  Circumferences,  Circles,  Squares,  Cubes,  Square 
Roots,  and  Cube  Roots.   


Circum- 
lercnce  of 
diameter  n. 

Surface  of 
diameter  n. 

Squares 

1  * 

Cubes 
n'. 

Square 

Cube 

3'H 

°'79 

I 

I 

1  "OOO 

I  "OOO 

0  25 

3-I4 

4 

5 

1-414 

1-259 

942 

707 

9 

27 

1732 

I  442 

12-57 

12-57 

16 

64 

2 -ooo 

1*587 

I5*7i 

19-63 

25 

I25 

2-336 

15  55 

25  27 

3° 

216 

2-449 

1  517 

2T99 

35  45 

49 

343 

2*635 

1-912 

25'13 

50-27 

04 

512 

2  525 

2  000 

25  2/ 

63-62 

51 

729 

3  000 

2' 080 

31-42 

75  54 

IOO 

1 ,000 

3-162 

2*154 

34'56 

95'03 

121 

I,33I 

3'3l6 

2-223 

377° 

1 13*10 

I44 

1,728 

3*464 

2  259 

40  84 

13273 

169 

2,179 

3*605 

2*35! 

4398 

15394 

196 

2,744 

3*741 

2410 

47-12 

1 76*7 1 

225 

3,375 

3872 

2  4OO 

50-27 

201  -06 

250 

4,096 

4-000 

2519 

53'4i 

226-98 

259 

4,9 1 3 

4'123 

2-571 

56'55 

254'47 

324 

5»832 

4-242 

262O 

59'69 

283'53 

36l 

0,059 

,,..0 
4  35o 

2  005 

02  53 

314-16 

4OO 

8,000 

4-472 

2-714 

«5'97 

,  - 
34o  30 

44 1 

- 

9, 2D  I 

4  5°2 

2  755 

3°°  l3 

aHa 

454 

10,648 

4*690 

2' 802 

72-26 

41548 

529 

I2,l67 

4*795 

2*843 

75-40 

45239 

576 

13,824 

4-898 

2-884 

78  54 

490-87 

625 

!5»625 

5000 

2924 

51  05 

53°'93 

070 

J7.576 

5"°99 

2-962 

04  02 

572"56 

729 

in 

I9,053 

5-196 

3  000 

57  90 

615-75 

7»4 

21,952 

5291 

3036 

911  I 

660*52 

54  I 

24,309 

D  30I 

3-072 

94 '2  5 

7OO  50 

900 

27,000 

5*477 

3107 

97-39 

75477 

90  I 

29,791 

5-507 

3  x4i 

100-53 

804*25 

1,024 

32,705  ; 

5 

3-174 

10367 

855-3o 

1,089 

35,937 

5*744 

3-207 

106-81 

907-92 

1,156 

39.304 

5830 

3-239 

10996 

962-1 1 

1,225 

42,875 

5-916 

3-271 

113-10  1 

1017-88 

1,296 

46,656 

6  000 

3  30I 

1 1624 

107521 

1,369 

50,653 

6-082  1 

3  332 

1 1938 

1134-11 

1.444 

54,872 

6- 1 64  ; 

3*36l 

12252 

1 194*59 

I.52I 

59,319  1 

6244 

3  391 

125-66 

125664 

1,600 

64,000 

6324 

3419 

581 


APPENDIX. 


Table  of  Circumferences," Circles,    quares,  Cubes,  Square 
Roots,  and  Cube  Roots. 


n. 

Circum- 
ference of 
diameter  n. 

Surface  of 
circle  of 
diameter  n. 

Squares 

Cubes 
n3. 

Square 
roots 
Vn. 

Cube 
roots 

41 

I28-80 

1320*25 

1,681 

68,921. 

6*403 

42 

I3rQC 

I  38C/44 

I.764 

74,088 

6-480 

0  '+/*-' 

43 

i35"°9 

I452-20 

1,849 

79,507 

6-557 

3-503 

44 

138-23 

I520-53 

i,936 

85,184 

6-633 

3-530 

141*37 

IC0O*43 

2,025 

91,125 

6-708 

3-  C  C6 

46 

I  Ad*1!  I 

166190 

2,1 16 

07.3^6 

6-782 

rc83 

4.7 

147-61; 

1734*04 

2.20Q 

103,823 

6-8cc 

3-608 

48 

150-80 

i8oq-i;6 

2, 304 

1 10,  CQ2 

6*928 

4Q 

1^3*04 
Do  y^r 

188C74 

2.4.0I 

I  I7.64Q 

/  1vlTy 

7*000 

t6co 

50 

157*08 

1963*49 

2,500 

125,000 

7-071 

3-684 

CI 

l60'22 

2042-82 

2,6oi 

132,651 

7-141 

3-708 

C2 

3 

163-36 

2I23'72 

2,704 

140,608 

7*21 1 

3*732 
O  /  D* 

53 

166-50 

2206*18 

2,809 

148,877 

7-280 

3756 

54 

169-65 

2290*21 

2,9l6 

157,464 

7-348 

3779 

cc 

I72-7Q 

1      1  y 

237C-83 

3,02c 

166, 37C 

7-416 

3-802 

56 

I75-93 

2463*01 

3,136 

175,616 

7-483 

3-825 

57 

17907 

2551-76 

3,249 

185,193 

7-549 

3*848 

58 

I82-2I 

2642-08 

3,364 

IOC., 1 12 

7'6ic 

3-870 

185-35 

2733*07 

3,481 

20'',  370 

7-681 

3-802 

60 

188-50 

2827*43 

•3,600 

216,000 

7-745 

3'0I4 

61 

IQI  "64 

2Q22'47 

3.721 

226,981 

7*810 

3*036 

62 

I94-78 

3019*07 

3,844 

238,328 

7-874 

3"Q57 

J  yj  1 

63 

I97-92 

31I7-24 

3,969 

250,047 

7'937 

3'979 

64 

20 1  06 

32I6-99 

4,096 

262,144 

8-ooo 

4-000 

6? 
j 

204-20 

33l8-3I 

4.22c 

274,62C 

8-062 

4'020 

66 

207-34 

342I*I9 

4,3t>6 

287,496 

8-124 

4-041 

67 

210*49 

3525'65 

4,489 

300,763 

8-185 

4-061 

68 

213-63 

3631-68 

4,624 

314,4^2 

8-246 

4-081 

69 

216-77 

3730*28 

4,761 

328,509 

8-306 

4-101 

70 

210*01 

"7  y 

3848-45 

4,900 

343,000 

8  366 

4-121 

71 

233-05 

3959*19 

5,041 

357,911 

8-426 

4-140 

72 

226-19 

4071*50 

5,184 

373,248 

8-485 

4*  1 60 

73 

229-34 

418539 

5,329 

389,017 

8-544 

4*179 

74 

232*48 

4300-84 

5,476 

405,224 

8-002 

4-198 

75 

235-62 

4417*86 

5,625 

421,875 

8-660 

4-217 

76 

238-76 

4536*46 

5776 

438,976 

8-717 

4-235 

77 

241-90 

4656*62 

5,929 

456,533 

8774 

4-254 

78 

245-04 

4778-36 

6,084 

474,552 

8-831 

4-272 

79 

248*19 

4901*67 

6,241 

493,039 

8-888 

4-290 

80 

25I-33 

5026-55 

6,400 

512,000 

8-944 

4-308 

582 

II.  TABLES. 


Table  of  Circumferences,  Circles,  Squares,  Cubes,  Square 
Roots,  and  Cube  Roots. 


n. 



Circum- 
ference of 
diameter  n. 

Surface  of 
circle  of 
diameter  n. 

Squares 

n". 

Cubes 
n  • 

Square 
roo's 

Cube 
roots 

81 

25447 

5I53-00 

6,561 

53M41 

9-OCO 

4-326 

82 

257-61 

528102 

6,724 

551,368 

9055 

4*344 

83 

26075 

5410-61 

6,889 

571,787 

o-i  10 

4-362 

84 

263-89 

5541-77 

7,056 

592,704 

9.165 

4-379 

85 

267-03 

5674-50 

7,225 

614,125 

9-219 

4-396 

86 

270-18 

5808-80 

7,396 

636,056 

9-273 

4-414 

87 

273-32 

5944-68 

7,569 

656,503 

9327 

4-43I 

88 

276*46 

6082*12 

7,744 

681,472 

9386 

4-447 

89 

279-60 

6221-14 

7,921 

704,969 

9'433 

4'464 

90 

28274 

6361-72 

8, 100 

729,000 

9-486 

4481 

9i 

235*88 

6503-88 

8,281 

753,371 

9  539 

4-497 

92 

289-03 

6647-61 

8,464 

778,688 

9  591 

4-5I4 

93 

292- 1 7 

6792-91 

8,649 

8o4,357 

9'643 

4-530 

94 

2953I 

6939-78 

8,836 

830,584 

9695 

4-546 

95 

29845 

7088-22 

9,025 

857.375 

9746 

4-562 

96 

301*59 

7238-23 

9,216 

884,736 

9797 

4-578 

97 

304-73 

738981 

9,409 

912,673 

9-848 

4-594 

98 

307-88 

7542-96 

9,604 

941,192 

9899 

4-610 

99 

3 1  ro2 

769769 

9,801 

970,229 

9949 

4  626 

100 

314-16 

7853-98 

10,000 

1,000,000 

1 0000 

4-642 

Properties  of  the  Circle. 

Diameter  x  3- 141 59  =  circumference. 

,,  x   8862     =  side  of  an  equal  square. 

,,  x  7071     =    ,,     ,,     inscribed  square. 

,,        squared  x  7854     =  area  of  circle. 
Radius  X  6-28318  =  circumference. 

Circumference       ^  3-14159  =  diameter. 

,,  =  3-54  Varea  ot  circle. 

Diameter  =  1128  Varea  of  circle. 

Length  of  arc  =  number  of  degrees  x  -017453  radius. 
Arc  of  i°  to  radius  1  =  0  01 745329. 

,,     1/      ,,       1  —  00002908S. 

,,     1"      ,,  1=0-000004848. 
Volume  of  prism  and  cylinder  =   base  x  height. 
,,        triangle  and  cone    =  £  ,,     x  ,, 

583 


APPENDIX. 


Multipliers  to  facilitate  Rapid  Calculation. 


Area  of  circle  =■  diameter  squared  x  7854. 
„  X  -6366  =side  of  inscribed  square. 


Avoirdupois  pounds  x 
x 
x 

x 
x 
x 

,,  inches  x 
Circumference  of  circle 


Cubic  inches 


feet 


Diameter  of  circle 


French  tonnes 
metres 
„  litres 

hectolitres 
„  grammes 
,,  kilogrammes 
Feet  per  second 
Gallons 
Grains 

Miles  per  hour 
Pounds  avoirdupois 


troy 

avoirdupois 


on  sq. 


inch 
foot 

Square  root  of  area 


of  diam.  of  sphere  x 


•009      =  cwts. 
•000455  ==  tons. 
•00058   =  cubic  feet. 
•01638   =  litres. 
•03705    —  cubic  yards. 
6-232     =  imperial  gallons. 
•003607  = 

=  diameter  x  3'i4i6. 
•2251     —  side  of  inscribed  square. 
•2821     =     „      equal  square. 
•3 1 83 1   =  diameter. 
3-1416   =  circumference. 
•7071     =  side  of  inscribed  square. 
•8862     =       „     equal  square. 
•984      =  English  tons. 

3-  281     =       „  feet. 
•2202     =  imperial  gallons. 
2-7512   =  English  bushels. 
•002205  =  lbs-  avoidupois. 

2-  205     =  „ 

•682       =  miles  per  hour. 

4-  541     =  French  litres. 
•001429  =  lbs.  avoirdupois. 
•1467     =  feet  per  second. 
7000     =  grains, 

•82286   =  lbs.  troy. 

1*2153   ==  lbs.  avoirdupois. 

•009      =  cwts. 

•00045    —  tons. 

144       =  lbs.  per  sq.  foot. 

•007       =  ,,  inch. 

1*12837  ==  diameter  of  equal  circle. 

3-  1416   =  convex  surface. 

584 


II.  TABLES. 


Logarithms. 


N. 

0 

1 

2 

1  3 

4 

5 

6 

7 

8 

9 

D. 

10 

0  ooo 

043 

086 

128 

170 

212 

253 

294 

334 

374 

40 

i 

414 

453 

492 

53i 

569 

607 

645 

682 

7'9 

755 

37 

2 

79 1 

828 

864 

899 

934 

969 

004 

038 

072 

106 

33 

1 
J 

206 

271 

101 

3QQ 

420 

4 

461 

492 

523 

553 

584 

614 

644 

673 

703 

732 

29 

5 

76l 

79O 

818 

847 

875 

9°3 

93 1 

959 

987 

014 

27 

6 

2  04I 

O68 

122 

I48 

17c 

ID 

201 

227 

J  j 

279 

2? 

7 

J  1 

JO 

JJJ 

380 

40; 

430 

480 

504 

529 

24 

8 

j  j  j 

S77 

601 

62; 

648 

672 

6ck 

718 

742 

765 

21 

9 

788 

8lO 

833 

856 

878 

900 

923 

945 

967 

989 

21 

20 

3  010 

032 

°54 

075 

O96 

ll8 

*39 

160 

l8l 

20I 

21 

i 

222 

243 

263 

284 

304 

324 

345 

365 

385 

404 

20 

2 

424 

444 

464 

483 

502 

522 

54i 

560 

579 

598 

19 

3 

617 

636 

655 

674 

692 

711 

729 

747 

766 

784 

18 

4 

802 

820 

838 

856 

874 

892 

909 

927 

945 

962 

17 

5 

979 

997 

014 

0? 

O48 

O65 

082 

099 

u6 

133 

17 

6 

4  150 

166 

183 

200 

2l6 

232 

249 

265 

281 

298 

16 

7 

3l4 

330 

346 

362 

378 

393 

409 

425 

440 

456 

16 

8 

472 

487 

502 

518 

533 

548 

564 

579 

594 

609 

15 

9 

624 

639 

654 

669 

683 

698 

713 

728 

742 

757 

14 

30 

771 

786 

800 

814 

829 

843 

857 

5Z.1 

886 

900 

M 

i 

914 

9?8 

942 

955 

969 

983 

997 

on 

024 

038 

13 

2 

5051 

065 

079 

092 

105 

119 

132 

145 

159 

172 

'3 

3 

185 

198 

21 1 

224 

237 

250 

263 

276 

289 

302 

»3 

4 

3i5 

328 

340 

353 

366 

378 

39 » 

403 

416 

42S 

»3 

5 

441 

453 

465 

478 

490 

502 

514 

527 

539 

55i 

12 

6 

563 

575 

587 

599 

611 

623 

635 

647 

658 

670 

12 

7 

682 

694 

705 

717 

729 

740 

752 

763 

775 

786 

12 

8 

798 

809 

821 

832 

843 

855 

866 

877 

888 

8_9? 

12 

9 

911 

922 

933 

944 

955 

966 

977 

988 

999 

010 

1 1 

N. 

0 

1 

2 

3 

4 

5 

6 

7 

9 

585 


APPENDIX. 


tn 
M 
u 
a 

6 
u 

With  excess  of  salt, 
although  very  in- 
tense, still  less  so 
than  with  excess  of 
silver. 

Scarcely  more  in- 
tense with  fuming 
than  without. 

Fuming  scarcely  in- 
creases the  inten- 

LesJintense  thanNo. 
i,  the  normal  paper  : 
scarcely    more  in- 
tense with  fuming. 

Paper  prepared  ac- 
cording to  Abnej-'s 
process. 

The    papers  attain 
nearly     the  very 

B.  With 
Ammonia  fuming. 

Colour  and 
Intensity. 

violet, 
v.  i. 

bluish  grey, 
n.  i. 

yellowish  grey, 
n.  i. 

SS3U3AI5lSU3g 

§        §,Ki        i  I 

A.  Without 
Ammonia  fuming. 

Colour  and 
Intensity. 

violet, 
v.  i. 

bluish  grey, 
n.  i. 

yellowish  grey, 
n.  i. 

•ooi  =  d3vjo 
ss3u3ai1isu3c} 

§>                     £           %            1                       i  I 

B.  With 
monia  fuming. 

Colour  and 
Intensity. 

blue  black,  more 

intense  than 
without  fuming 

b  si)  grey, 
n.  i. 

reddish  grey, 
n.  i. 

violet,  with  a 
red  tinge, 
v.  i. 

Intense, 
equal  to  normal 
No.  i. 

violet, 
v.  i. 

Am 

•°°i  =  ID3vJO 

SS3U3ApiSU9C; 

o              o        o        o              o  o 

O                    0           lO          O                    CO                   o  ■ 

M                            Os                                 H                            H  M 

A.  Without 
Ammonia  fuming. 

Colour  and 
Intensity. 

blue  black, 
v.  i. 

bluish  grey, 
n.  i. 

greenish  grey, 
n.  i. 

violet,  with 
red  tinge, 
v.  i. 

Intense,  very 
nearly  equal  to 
the  normal, 
No.  i. 

violet, 

v.  i. 

•o°i  =  ID2v  J° 
ssouoai;tsu3S 

2         a  •  1 '  '  3        £  § 

Name. 

Chemical 
Formula 
(Solubility). 

1.  Silver  Chloride  : 

AgCl  (insol.) 

2.  Silver  Bromide : 

AgBr  (insol.) 

3.  Silver  Iodide  : 

Agl  (insol.) 

4.  Silver  Chloride  : 
AgCl;  excess  of  silver 
nitrate  removed  by 

washing. 

5.  Silver  Chloride  : 
AgCl  treated  as  in  4, 
and  then  floated  on 

KN02  solution. 

6.  Silver  Chloride  : 
AgCl,  prepared  as  No. 
5,  but  Sodium  Sul- 
phite used. 

586 


II.  TABLES. 


9  i?  91  >,     V  «j  4)  g      «'i  C  "O  1,1 

rtXe"S     §S5'c  -eg 
K     ,2  o      rt      0-b/cw     Xi  P 

ST""*      21-  4;  hew: 

fij2«i2s§*s:«§rses-a 

cS    u      =  £  .2  <« -n  F  <"  ii 


2  a)  *■  «  2  ?  „, 
c/3  H 


«  r  o 
a.?  <«  • 

^     rt  o 


C 

3.M 


's  Ba. 

i/i 

r—  Cu  u. 


C  4)  u 

o  2ir 

(0 


J2  S." 

5s 


rt  <u 


o 

in! 


p 

5  •» 


>  c 
o 


p._- 

JO  » 


3  B 

T3 


MM 
Ifi 

•a 
•a 


3  "5 


O  . 
'I 

«j  s 


*  E 
■a 


00 

o 

£  1 

1  8 

o 

N 
M 

00 

xT 

•own, 

own, 

E 

be 

a 

> 

ellow, 

i  red, 

own, 

reddii 
n.  i. 

1-  V} 

ja  — 
> 

"a 

pie  bi 
v.  i. 

— 

lowisr 
s.  i. 

red  bro 
s.  i. 

X" 
A  £ 
.2 

lowisl 
n.  i. 

)let  br 
m.  i 

ind 

a 

yell 

red( 

"o 

>> 

> 

VO 

m 

0 
m 

R  1 

1 

o 

CO 

00 

fi  53  iT-d  S3  fi  o   »  -         ka  O 

fi       18  «  dS.  1  »       t&  »R  :* 

«  3  m     «  h     -T.x  fiU~  fiU~ 

£  5    i)  T3  a.  ®"P  "5  »;*       -~   55  SI'S  SI* 

b|     fell  :S1  II  IS  go    la  n  e£c  fie  f|« 

WOT  .  .  '<.<.<  ,U  .tt 

CO  O  M  II  M  HIM>-  ~  M l_  ~ 


587 


APPENDIX. 


IS 


S.3 


u 

Is 


•ooi=i33v  jo 

SS3U3AUtSU3g 


CO  -O  3  O 

<u  J3  <u  _  cu  rt 


o 


be 

si 


< 


o 


-o  So 
^  be 


3£ 


ssauPAuisuac; 


2,  6 


.  c 

20  O 

6 
< 


. 


o  « 
o  c 


SS3U3AI}TSU3S 


2,3 


.  o 

< 


O  B 

U"1 


ho  C 


13  be- 
B  * 


o 


•ooi=lD2vjo 
ssaaaAijisuag 


s  s2 


O  « 

••-iD. 


o 


51 

3  2 
.  be 


co 

Si 

13  2 

.  be 
2>< 


588 


II.  TABLES. 


o  o 
•z:  c 

o  3" 


c  fa 


£  2 
o 


3  5 


"O'O  > 

a  2  9 


13  *J  U, 


u  o  "  s  I 
a,  «i  r:  «  — 

■Si**0* 

■SSI-S-Slsi 


(/>  to 


p 


ish, 

h 
u 
be 

in 

red, 

red, 

yellow 
n.  i, 

greenish 
s.  i 

brown 

6.  i, 

yellow 
t.  i. 

2.  ** 
13 

>i 

in 

VO 

o 


t  S 
c/yj 

b/5 


o 
o 
u 

a 


OS 

O  3 

.-Si 

<•  o 


O 

y 
o 

s  . 

..or 

<j>t*  w 

^5 


O 
O 

..u 

«E 

go 
zx 

JSCJ 

Is 


s  - 


o  I 

SOS 
«^ 

3J* 


2oj 


,  o 

MX 

fitf 


2Ue 


 bX 

1$ 

X  u 


589 


APPENDIX. 


Table  of  the  Formulae  of  Chemicals  used  in  Photography. 


Formula. 

Molecular 
Weight. 

Acid,  Acetic  

HC„H302 

60 

,,    Boracic  or  Boric 

h;bo3" 

62 

Carbolic... 

HC6HeO 

94 

,,  Citric   

H3C6H507,  H,0 

210 

Formic  ... 

HCHO, 

46 

Gallic  ...   

HC7H503 

170 

„  Hydrobromic  

HBr 

81 

Hydrochloric  

HC1 

36-5 

,,  Nitric   

HN03 

63 

, ,  Oxalic  

H2C204,  2H20 

126 

Pyrogallic 

H3C6H303 

126 

Salicylic  

HC7H503 

138 

,,  Sulphuric 

H2S04 

98 

Sulphurous   

H2S03 

82 

Tannic  ... 

H4CtfHi8Ol7 

618 

,,  Tartaric  

H4C4H206 

15o 

Alcohol  

C2H5HO 

46 

„  Methyl   

CH3HO 

32 

Alum  

A12(S04)3,  K,S0424H20 

948 

, ,  Chrome  

Cr,(S04)3K2S04.  24H;o 

999 

Ammonia  ... 

NH3 

17 

Ammonium  Bichromate 

(NH4)2Cr207 

253 

,,        Bromide ... 

NH4Br 

98 

, ,  Carbonate 

NH4HC03,  NH4C0,NH, 

175 

,,  Chloride  

NH4Ce 

535 

, ,  Iodide   

NH4I 

145 

,,  Nitrate  

NH4N03 

80 

„  Oxalate  

(NH4)2C204 

124 

,,  Sulphide... 

NH4HS 

5i 

,,        Sulphocyanide  ... 

NH4CNS 

76 

Barium  Bromide 

BaBr2 

297 

„  Chloride   

BaCl,,  2H,0 

244 

Iodide  

Bal, 

39i 

Nitrate 

Cadmium  Bromide   

Ba(NO"3)2 

261 

CdBi^Hp 

344 

,,       Chloride  ... 

CdCL, 

183 

Iodide   

Cdl," 

366 

Calcium  Bromide 

CaBr24H,0 

272 

Carbonate  ... 

CaCOs 

100 

„  Chloride   

CaCl2 

in 

Iodide 

Cal, 

294 

Calcium      Hypochlorite,  or 

Chloride  of  Lime  .. 

CaCl20,CaCl, 

254 

590 


II.  TABLES. 


Formula. 

Molecular 
Weight. 

Copper  Acetate 

Cu(C3H30.,)  H  0 

200 

„  Bromide   

CuBr., 

223-4 

„  Chloride 

CuCLH20 

171 

Sulphate 

CuS04*5H,0 

249 

and  Ammonium  Sul- 

phate 

CuS044NH3 

245-5 

Glycerine   

C3H.,(HO)3 

92 

Gold  Perchloride 

AuCl, 

3025 

Ilydroquinone 

C6H42HO 

no 

Hydroxylamine  Chloride 

NH3OHCl 

— 

Iron  Chloride  (ferrous) 

FeCl, 

127 

,,        „  (ferric)  

Fe2Cf6 

325 

.,   Citrate  ..   

Fe2(C6H,07)3 

598 

„  Iodide   

Fel, 

3IO 

„  Nitrate  

Fe(N03).,6II20 

288 

,,    Oxalate  (ferrous) 

FeC204  ' 

I44 

„  (ferric)  

Fe2(C,04)3 

370 

,,    Sulphate  (ferrous) 

FeS04,  7ll,0 

278 

(ferric) 

Fe,(S04)3 

4OO 

,,    Ammonia  Sulphate 

FeS04,  (NH4)2S046ILO 

392 

Lead  Acetate  ... 

Pb(C,H3023),H,0 

379 

,,  Carbonate 

Pb(C03,  Pb(HO), 

774 

Iodide   

Pbl2 

460 

,,  Nitrate  

P1)(N03), 

33i 

,,    Oxide  ...   

PbO 

223 

Lithium  Bromide 

LiBr 

87 

,,  Chloride 

LiCl 

42'5 

,,  Iodide 

Li  I 

134 

Magnesium  Bromide  ... 

MgBr 

1X4 

Chloride  ... 

MgCL 

95 

Iodide 

Mgl2 

278 

,,        Sulphate  ... 

MgSOjILO 

246 

Mercury   Chloride  (mercuric) 

HgCL 

271 

,,  (mercurous) 
Cyanide   

HgCl 

235-5 

HeCy, 

252 

,,      Iodide  (mercuric)  ... 

Hgl, 

454 

,,         ,,     (mercurous)  ... 

Hgl 

327 

Platinum  Chloride   

PtCL 

339 

Potassium  Bicarbonate 

KHCO3 

100 

Bichromate 

K.,Cr.,07 

294-6 

I  >1  1        |i  u        ...  ... 

l\  1  )1 

1 191 

,,  Carbonate  

K,C03 

138-2 

Potassium  Chlorate   

KC103 

1224 

,,  Chloride  

KC1 

745 

,,        Chloro-platinite  ... 

488-4 

, ,  Citrate   

K3Cf(IL,07H20 

324  3 

Cyanide   

KCN 

65 

59i 


APPENDIX. 


Potassium  Ferricyanide 
, ,  Ferrocyanide 
, ,        Hydrate    . . . 
Iodide 
'  Nitrate 
, ,  Permanganate 
,,  Sulphocyanide 
Silver  Acetate 
Bromide 
, ,  Carbonate 
Chloride 

Citrate  

Fluoride 
Iodide  ... 

,,  Nitrate  

,,  Nitrite  

Oxalate 
Oxide  ... 
, ,  Sulphide 
Sodium  Acetate 

„      Biborate  (Borax) 

Bromide 
,,      Bicarbonate  ... 
,,  Carbonate 
„  Chloride 
Citrate 
Hydrate 
,,  Hyposulphite 
„  Iodide 
Nitrate 
„  Sulphantimonite 
Sulphate 
Sulphide 
„  Sulphite 
Strontium  Bromide  ... 
,,       Chloride  ... 
Nitrate 
Tin  Chloride  (Stannic) 
,,        „  (Stannous) 
Uranium  Bromide 
„  Nitrate 
„  Sulphate 

Zinc  Bromide  

Chloride  ... 

„  Iodide   

,,  Nitrate   

,,  Sulphate  


Formula. 


K4FeC6Ne3HsO 
KHO 
KI 
KN03 
K2M203 
KCNS 
AgC,,H302 
AgBr 
Ag2C03 
AgCl 
Ag3C6H507 
AgFl 
Agl 
AgN03 
AgNO, 
Ag2C204 
Ag20 
Ag2S 
NaC,H30.„  6H,0 
Na,B407ioH,6 
'  NaBr 
NaHC03 
Na9C03ioHX> 
"  NaCl 
NagCflH507 
NaHO 
Na,S.,035H20 
*  Nal 
NaN03 
NaSbS3 
Na2S04ioH20 

Na2S9H,0 
Na2S037H20 
SrBr26H,0 
SrCl26H;0 
Sr(N03), 
SnCU 
SnCl22H20 
UBr^HaO 
UO,(N03)26H,0 
Ua(S04)3H,b 
ZnBr., 
ZnClJ 
Znl2 
Zn(N03)26H,0 
ZnS04,  7H,6 


592 


II.  TABLES. 


Usual  Sizes  of  French  and  Italian  Dry  Plates. 


French.  Inches. 


64  bv 

9  Centimetres  ... 

...    2-;  by 

37 

9  »l 

12         ,        ...  ••• 

...    37  ,, 

47 

T  C 

xj         n         ...  ... 

...    47  „ 

5 '9 

l  1 

18 

...     31   , , 

/  ** 

12  , 

20 

...    47  „ 

7-8 

I  c 

21         ,,        ...  ... 

j  y    1 » 

8-2 

22  11 

•  ■  •      J  y  i) 

8-6 

18 

9/1 

7-0 

21  „ 

27  „   

...    8-2  „ 

106 

24  II 

3°   

•  ••    9'4  n 

T  I  -8 

27  M 

33  ■> 

...  io-6 

12-9 

27  M 

35  m   

...  io*6 

137 

30  M 

40   

...  ir8 

157 

40  1, 

50   

...  157  „ 

19-6 

60   

...  19*6  „ 

23-6 

Italian. 

Inches. 

9   by  12  Centimetres 

...    37  by 

47 

12  „ 

16  ,  

•  47 

6-3 

12  ,, 

18  „   

•••    47  11 

13  M 

18  „   

...    5'i  » 

7-0 

12  „ 

20   

47  m 

7*8 

18  „ 

24   

...    70  M 

9-4 

21  „ 

27  „   

...    8-2  „ 

io*6 

24  » 

30   

•••    9'4  ,. 

1 1-8 

27 

33   

...  io-6 

129 

30  „ 

36   

...  1 1  S  „ 

141 

40  11 

5o   

...  157  - 

19^) 

50  „ 

60   

...  i9'6  „ 

236 

Sizes  of  Glass,  Mounts,  Paper,  Etc. 

Petite  cards    1'  by 

One-ninth  plate          ...       ...       ...  2     „  2.\ 

One-sixth  plate          ...    3|    ,,  3] 

One-fourth  plate         ...       ...       ...  3]    „  4] 

Half  plate   4}  Jay  6$  and  4]  5 1 

593  QQ 


APPENDIX. 

Sizes  of  Glass,  Mounts,  Paper,  Etc.  {continued). 

Half  plate  (English)   4f   „  6£ 

Whole  plate  (4-4)   6£  U 

Extra  4-4    ...    8     ,,  io 

Other  sizes  are  expressed  by  inches. 

Sizes  of  Mounts. 


Stereoscopic  3|  by  7, 4  by  7, 4^  by  7,  4^ 

by7,  5  by  8 

Victoria 

3i  by 

5 

Imperial   

7|  „ 

9* 

Boudoir   

Si  H 

»i 

Panel  ...   

4  M 

Minette   

I!  M 

2| 

Card 

4  „ 

4* 

Cabinet   

4i  M 

6i 

Promenade 

4i  „ 

74 

Sizes  of  Albumen  Paper. 

18  by  22f,  2o|  by  24^,  22  by  36,  26  by  40,  27  by  42 
Sizes  of  blotting  paper    19  by  24 

Freezing  Mixtures. 

Reducing  the  Temperature  From  To 

parts.  Degrees  C         Degrees  C. 

3  Nitrate  of  sodium  +  4  water         ...    +13-2         —  5-3 

9  Phosphate  of  sodium  +  4  dilute  nitric 

acid   +10  —  9 

3  Sulphate  of  sodium  +  2  dilute  nitric 

acid   +  10  — 10 

1  Nitrate  of  sodium  +  4  water   — io-6 

1  Chloride  of  potassium  +  4  water  — 11 -8 

5  Sal-ammoniac  +  5  saltpetre 

8  Sulphate  of  sodium  +  5  cone,  sul- 
phuric acid   +10  — 17 

1  Sulphocyanate  of  potass.  +  1  water    +  18  — 21 

1  Chloride  of  sodium  +  3  snow   — 2 1 

1  Sal-ammoniac  +  1     saltpetre  +  1 

water         ...       ...       ...       ...     +8  — 24 

3  Crystal,  chloride  of  calcium  +  1  snow   —36 

1  Snow  4-  1  dilute  sulphuric  acid     ...    —  5  — 41 

594 


II.  TABLES. 


Table 

of  Elements 

Name. 

Atomic  weight. 

/\tuminiurii  ... 

Antimony 

T  OCX 

Arsenic  ... 

75 

oarium  ••• 

l37  43 

"R "  cm  n  tVi 
JDlcjiHUUl  ... 

208  "9 

Boron 

1 1 

Rrnminp 

Ul  KJHHLIKZ  ... 

1    £1  H  TT1 1 11TTI 

<od  LUIll  UIII  ... 

112 

Calcium 

40 

Carbon 

12 

Cerium 

140*2 

Chlorine 

Chromium 

t",2'I 

Iron  ... 

jw 

Lanthanum 

1^8-2 

Lead 

www  y  5 

Lithium 

7'02 

■^4  3 

Maneranp^p 

cc 

Mercnrv 

200 

Molvbdpmim 

UUV^l.  11111 

Neodymium... 

i4ot; 

Nickel 

c;8-7 

Nitrogen 

...         1  "-"J 

Osmium 

1  no-8 

Oxygen 

16 

Palladium  ... 

...  1066 

Phosphorus ... 

...  31 

Platinum 

...  195 

Potassium   . . . 

...  39-u 

Praseodymium 

...  1435 

Rhodium 

...  103 

Rubidium    . . . 

...  85-5 

Ruthenium  ... 

...  ior6 

Samarium  ... 

...  150 

Name. 

Cobalt 

Columbium 

Copper 

Erbium 

Fluoride 

Gadolinium. 

Gallium 

Germanium 

Glucinum 

Gold... 

Hydrogen 

Indium 

Iodine 

Iridium 

Scandium 

Selenium 

Silicon 

Silver 

Sodium 

Strontium 

Sulphur 

Tantalum 

Tellurium 

Terbium 

Thallium 

Thorium 

Thulium 

Tin  ... 

Titanium 

Tungsten 

Uranium 

Vanadium 

Ytterbium 

Yttrium 

£inc  ... 

Zirconium  . 


Atomic  weight 
...  59 
...  94 
...  636 

...  1663 
...  19 

...  I56'I 
...  69 
...  723 

9 

...  197*3 
roo8 

...  ii37 

...  126-85 

...  193-1 

...  44 

...  79 
...  28-4 

...  10792 

...  2305 

...  87.6 

32*06 

...  1826 

...  125 

...  160 

...  204-18 

...  232-6 

...  1707 

...  119 

...  48 

...  114 

...  2396 

...  5*-4 

...  173 

...  891 

...  65-3 

906 


PAGES 

597 
598 


IV.  SYNONYMS. 


A. 

Abdruck.  Ger.  Print,  impression. 
Aberration.  Fr.,  Ger.  Aberration. 
Abschwacher.    Ger.  Reducer. 

Abziehpapier.    Ger.    Stripping-paper,  transferotype. 
Accelerateur.    Fr.  Accelerator. 
Accessoire.    Fr.  Accessory. 
Acetate.    Fr.  Acetate. 

Achromatische  Linse.    Ger.    Achromatic  lens. 
Achromatisme.    Fr.    \   .  , 
Achromatism™.    Ger.  I  Achromatism. 
Acide.    Fr.  Acid. 
Acide  azoteux.    Fr.    Nitrous  acid. 

„     azotique.    Fr.    Nitric  acid. 
Actinique.    Fr.  Actinic. 
Adragant.    Fr.  Tragacanth. 
Aethylather.    Ger.    Ether,  ethylic  ether. 
Aetzammoniak.    Ger.    Caustic  ammonia,  Liq.  amm.  *88o. 
Aetzkali.    Ger.    Caustic  potash. 
Aetzkalk.    Ger.  Quick-lime. 
Aetznatron.    Ger.    Caustic  soda. 
Affaiblir.    Fr.    To  reduce. 
Agrandissement.    Fr.  Enlargement. 
Aktinisch.    Ger.  Actinic. 
Alabaster verfahren.    Ger.  \ 
Albatre,  precede  d'.     Fr. )  A1:lbaste»-  Process- 
Alaun.    Ger.  Alum. 

Albertypie.    Fr.,  Ger.    Albertype,  collotype. 

Albumin.    Ger. } 

.  r  Albumen. 

Albumme.    Fr. ) 

Albuminat.  Ger  A 
...      .  „    /  Albuminate 

Albuminate.    Fr. ) 

599 


APPENDIX. 


Albuminpapier.    Ger.    Albumen  paper. 

„      verfahren.    Get:     „  process. 
Alcali.  Fr. 
Alkali.  Ger. 
Alcool.  Fr. 
Alkohol.  Gey 


}  Alkali. 

,} 


Alcohol. 


Aldehyde.    Fr.,  Ger.  Aldehyde. 

Alun  d'ammoniaque.    Fr.    Ammonia  alum. 

„    de  chrome.    Fr.    Chrome  alum. 

Ambre  jaune.    Fr.  Amber. 

Ameisensaure.    Ger,    Formic  acid. 

Amidon.    Fr.  Starch. 

„      grille.    Fr.  Dextrin. 

Ammoniaque  liquide.    Fr.  \ 

A         .  .      ^  r  Ammonia. 

Ammomak.    Ger.  J 

„        Raucherung.    Ger.    Ammonia  fuming. 

Ampoule.    Fr.  Blister. 

Anascope.  Fr.\ 

Anaskop.  Ger  J  Focussing  magnifier. 
Anilindruck.    Ger.    Aniline  printing. 
Anreiber.    Ger.    Roller  squeegee. 

Anthracotypie.    Fr.,  Ger.    Anthracotypc,  a  powder  process. 
Antimoine  gris.    Fr.    Sulphide  of  antimony. 
Aplanatisch.    Ger  A  , 
Aplanetique.    Fr.  )  APlanatlc- 
Apparat.    Ger.  \  . 
Appareil.    Fr.  J  APParatus' 

„      d'atelier.    Fr.    Studio  camera. 

„      automatique  pour  l'impression.    Fr.    Automatic  printer 

„      de  campagne.    Fr.    Tourist  camera. 

„      detective.    Fr.    Detective  camera. 

,,      a  main.    Fr.    Hand  camera. 

„      panoramique.    Fr.    Panoramic  camera. 

Appui-tete.    Fr.    Head  rest. 

Aqua-vernis.    Fr.    Water  varnish. 

Araometer.    Ger.  \ 

.  ,  „         }  Hydrometer. 

Areometre.    Fr.      )  J 

Argent.    Fr.  Silver. 

„     come.    Fr.    Horn  silver,  or  silver  chloride. 

Argentometer.    Ger.  \ 

aTO    A  „     }  Argentometer. 

Argentometre.    Fr.  )  & 

Aristogen.    Ger.}  . 

»•».    «■         7-    r  Aristogen,  q.v. 

Aristogene.  Fr.) 

600 


IV.  SYNONYMS. 


Aristopapier.  Ger.\ 

Aristotype.       Ger.  V  Gelatino-chloride  emulsion  printing-out  papers. 

Aristotypie.     Fr.  J 

Asphaltfirniss.    Ger.    Asphalt  varnish. 

verfahren.    Ger.    Asphalt  process. 
Astigmatismus.    Ger.  Astigmatism. 
Atomgewichte.    Ger.    Atomic  weight. 
Aufnahme.    Ger.  Exposure. 
Aufnahmeperson.    Ger.  Operator. 
Aufziehen.    Ger.    To  mount. 

Augensblickbilder.    Ger.    Instantaneous  picture,  snapshot. 

,,        verschluss.    Ger.    Instantaneous  shutter. 
Aurate  d'ammoniaque.    Fr.    Fulminating  gold. 
Aureole.    Fr.    Halo,  or  halation. 
Auscopiren.    Ger.    To  print  out. 
Ausrustung.    Ger.    Complete  outfit. 
Aussenaufnahmen.    Ger.    Outdoor  photography. 
Autotype.    Ger.  j  Process.block  makjng< 
Autotypie.    Fr.  ) 
Azotate.    Fr.  Nitrate. 
Azote.    Fr.  Nitrogen. 
Azotite.    Fr.  Nitrite. 


Bad.  Ger.\ 
Bain.   Fr.  f 


B 

Bath. 


„    a  clarifier.    Fr.    Clearing  bath. 

„    fixateur.    Fr.    Fixing  bath. 

,,    virage.    Fr.    Toning  bath. 
Balance  cuvette.    Fr.    Rocking  dish. 

,,      hydrostatique.    Fr.  Hydrometer, 
Balg  Auszug.    Ger.    Bellows  body. 

,,    Camera.    Ger.    Bellows  camera. 
Barytpapier.    Ger.    Baryta  paper. 
Bascule  du  chassis.    Fr.    Swing  back, 
Baserigide.    Fr.  Baseboard. 
Baume  du  Canada.    Fr.    Canada  balsam. 
Bee  a  gaz  Auer.    Fr,    Incandescent  gas  light. 
Beiwerk.    Ger.  Accessory. 
Beleuchtung.    Ger.  Lighting. 

„         schirm.    Ger.  Reflector. 
Belichtung.    Ger.  Exposure. 
Belmontine.    Fr.    Solid  paraffin  wax. 

601 


APPENDIX. 


Bergcry  stall.    Ger.  Quartz. 
Bergmehl.    Ger.    Infusorial  earth. 
Bernstein.    Ger.  Amber. 

„       saure.    Ger.    Succinic  acid. 
Beschleuniger.    Ger.  Accelerator. 
Beschneideglaser.    Ger.    Cutting  shape. 
Bichlorure  de  plomb.    Fr.    Lead  chloride. 
Bildfeld.    Ger.    Angle  of  view. 
Bildformate.    Ger.    Size  of  print. 
Bildmesser.    Ger.    View  meter. 
Bildsucher.    Ger.    View  finder. 
Bimstein.    Ger.    Pumice  stone. 
Bitume.    Fr.  Bitumen. 

„     iliquide.    Fr.  Naphtha. 
Blanc  d'Espagne.    Fr.  Whitening. 
Blanchir.    Fr.    To  bleach. 
Blancs.    Fr.  Whites. 

Blasebalgcamera.    Ger.    Bellowsbody  camera. 
Blasen.    Ger.  Blisters. 
Blaudruck.    Ger.    Ferroprussiate  printing. 
Blechcassetten.    Ger.    Metal  slides. 
Blechrahmchen.    Ger.    Metal  sheaths. 
Bleiacetat.    Ger.    Acetate  of  lead. 
Bleichkalk.    Ger.    Chloride  of  lime. 
Bleichlorid.    Ger.    Lead  chloride. 
Bleichwasser.    Ger.    Eau  de  Javelle. 
Bleizucker.    Ger.    Sugar  of  lead. 
Blende.    Ger.  Diaphragm. 
Bleu  de  quinoleine.    Fr.  Cyanine. 
Blitzlicht.    Ger.  Flashlight. 

Blutlaugensalz  gelbes.    Ger.    Yellow  prussiate  of  potash. 

„  rothes.    Ger.    Red  „  „ 

Bodenauszug.    Ger.  Baseboard. 
Boite  a  escamoter.    Fr.    Changing  box. 
Bombees.    Fr.    Cameo  prints. 
Bordure  noire.    Fr.    Safe  edge. 
Borsaure.    Ger.    Boric  acid. 
Braunstein.    Ger.    Black  oxide  of  manganese, 
Brennpunkt.    Ger.    Focus,  focal  point. 
Brennweite.    Ger.    Focal  length. 
Brenzcatechin.    Ger.  Pyrocatechin. 

Brillant  Albuminpapier.  Ger.  Double  albumenised  paper. 
Brillantwasser.    Ger.    A  thin  copal  and  benzole  varnish. 

602 


IV.  SYNONYMS. 


Brom.    Ger.  Bromine. 

„     ammon.    Ger.    Ammonium  bromide. 
,,     calcium.    Ger.  Calcium. 

„     eosinsilber.    Ger.    Eosinated  bromide  of  silver. 
„     kalium.    Ger.    Potassium  bromide. 
„     lithium.    Ger.    Lithium  bromide, 
natrium.    Ger.    Sodium  bromide, 
silber.    Ger.    Silver  bromide. 
Bromhydrate  d'ammoniaque.    Fr.  Ammonium  bromide. 
Bromsilbercollodium.    Ger.    Collodio-bromide  of  silver. 
„         gelatine.    Ger.    Gelatino-bromide  of  silver. 
„  „       papier.    Ger.    Bromide  paper. 

Bromure  de  chaux.    Fr.    Calcium  bromide. 
Bromwasser.    Ger.   Bromine  water. 

„    zink.    Ger.    Zinc  bromide. 
Broncirte  or  broncefarbene  Schatten.    Ger.    Bronzed  shadows. 
Brouillard  lumineux.    Fr.  Halation. 
Bruleur  de  Bunsen.    Fr.    Bunsen  burner. 
Brustbild     Ger.    Bust  portrait. 
Buchcamera.    Ger.    Book  camera. 
Bulles  d'air.    Fr.    Air  bells. 
Bunsenbrenner.    Ger.    Bunsen  burner. 
Buste.    Fr.    Bust  portrait. 

C. 

Cabinet  noir.    Fr.    Dark  room. 
Caches.    Fr.  Masks. 

Calcinirte  Soda.    Ger.    Anhydrous  sodium  carbonate. 

Calibres.    Fr.    Cutting  shapes. 

Camee-Bilder.    Ger.    Cameo  prints. 

Campher.    Ger.\  _ 

Camphre.    Fr.  J  CamPhor- 

Caoline.    Fr.  Kaolin. 

Caput  mortuum.    Lett.    Oxide  of  iron. 

Carbolsaure.    Ger    Carbolic  acid. 

Cartes  Russes.    Fr.    Vignettes  on  dark  ground. 

Cartouches.    Fr.  Cartridges. 

Cassette.    Ger.    Dark  slide. 

Cassettenschnapper.    Ger.    Dark  slide  spring  catch. 
Celloidin.    Ger.    Celloidin,  special  form  of  pyroxylin. 

„       papier.    Ger.    Collodio-chloride  paper. 
Celluloidschalen.    Ger.    Celluloid  dishes. 
Centralblende.    Ger.    Diaphragm  between  two  lenses. 

603 


APPENDIX. 


Centre  optique.    Fr.    Optical  centre. 
Centrifugir  Maschine.    Ger.    Centrifugal  machine. 
Cerat.    Ger.    Encaustic  paste. 
Ceresine.    Fr.    Solid  paraffin  wax. 
Cerotine.    Ger.  \  _  ,    _  , 


Chambre  binoculaire.    Fr.    Stereoscopic  camera. 

„       detective,    Fr.    Detective  camera. 

„       livre.    Fr.    Book  camera. 

„       noire.    Fr.    Dark  camera. 

„       a  main.    Fr.    Hand  camera. 

„       a  simple  ouverture.    Fr.    Pinhole  camera. 

n       a  soufflet.    Fr.    Bellowsbody  camera. 
Champ.    Fr.    Field  of  a  lens. 

or  nettete.    Fr.    Angle  of  view. 

„     plat.    Fr.    Flatness  of  field. 
Charbon.    Fr.  Charcoal. 

„      animal.    Fr.    Animal  charcoal. 
Chariot  droit.    Fr.  Baseboard. 
Chartotypie.    Ger.  Talbotype. 
Chassis.    Fr.    Dark  slide. 

„      double.    Fr.    Double  dark  slide. 

„      a  escamoter.    Fr.    Changing  dark  slide. 

„      a  imprimer.    Fr.    Printing  frame. 

,  multiplicateur.  Fr.  Multiple  dark  slide, 
a  rideau.  Fr.  Roller-blind  dark  slide, 
a  rouleaux.    Fr.    Roll  holder. 

„      triple.    Fr.    Dark  slide,  to  take  3  plates. 
Chaux  eteinte.    Fr.  Slake-lime. 

„     vive.    Fr.  Quick-lime. 
Chemigraphie.    Ger.    Zinc  etching. 

Chemische  oder  alkalische  Entwickelung.    Ger;   Alkaline  develop- 


Chlorammonium.    Ger.    Ammonium  chloride. 
„    barium.    Ger.    Barium  chloride. 
„    blei.    Ger.    Lead  chloride. 
„    calcium.    Ger.    Calcium  chloride. 

604 


Encaustic  paste  made  from  plant  wax. 


ment. 

Brennpunkt.    Ger.    Actinic  focus. 
„        Schleier.    Ger.    Chemical  fog. 
Chinolinblau.    Ger.  Cyanine. 

„      roth.    Ger.    Quinoline,  or  chinoline  red. 


IV.  .SYNONYMS. 


eisen.    Ger.    Iron  chloride. 
,,    gold.    Gcr.    Gold  chloride. 

kalium.    Ger.    Gold  and  potassium  chloride 
„      „  natrium.    Gcr.     „      „    sodium  chloride. 
„    iridium.    Ger.    Iridium  chloride. 
„    kalium.    Gcr.    Potassium  chloride. 

kalk.    Ger.    Lime  chloride. 
„    lithium.    Ger.    Lithium  chloride. 
„    magnesium.    Gcr.    Magnesium  chloride. 

natrium.    Gcr.    Sodium  chloride. 
„    platin.    Ger.    Platinum  chloride. 
„    quecksilber.    Gcr.    Mercuric  chloride. 
Chlorhydrate.    Ger.    Hydrochlorate,  or  chloride. 
Chlorsaures  Kali.    Ger.    Chlorate  of  potassium. 

„         Silber.    Ger.    Chlorate  of  silver. 
Chlorsilber.    Ger.    Chloride  of  silver. 

„         collodium.    Ger.    Collodio-chloride  of  silver. 
„         gelatine.    Gcr.    Gelatino-chloridc  of  silver. 
„       papier.    Ger.    Chloride  paper. 
Chlorstrontium.    Ger.    Strontium  chloride. 
„    wasser.    Ger.    Chlorine  water. 
„  stofFsaure.    Gcr.    Hydrochloric  acid. 

„    zink.    Ger.    Zinc  chloride. 
Chlorure.    Fr.  Chloride. 
Chromalaun.    Ger.    Chrome  alum. 

Chromatische  Aberration.    Ger.    Chromatic  Aberration. 

Chromgelatine.  Ger.\     T3.  ,  ,  . 

,  .        _         }    Bichromated  gelatine, 
leim.    Gcr.  J 

Chromo-Aristopapier.    Ger.    Baryta  paper. 

Chromophotographie.    Ger.    Crystolcum  painting. 

Chromsaure.    Ger.    Chromic  acid. 

Chromsaures  Kali,  einfaches.    Cn:    Potassium  chromate. 

m         .»        zweifaches.    Ger.    Potassium  bichromate. 
Cire.    Fr.  Wax. 
Citronensaure.    Ger.    Citric  acid. 

,,     saures  Eisenoxyd.    Ger.    Citrate  of  iron. 

n         >«  it        ammon.    Ger.    Ammonio-citrate  of  iron. 

„        ,,      Silber.    Ger.    Silver  c  itrate. 
Clair  de  lune.    Fr.    Moonlight  effect. 
Cliche.    Fr.  Negative. 
Cliches  poses.    Fr.    Time  exposure. 
Cliquet.    Fr.    Spring  catch  for  dark  slide. 
Collage.    Fr.  Mounting. 

605 


APPENDIX. 


Colle  d'amidon.    Fr.    Starch  paste. 

„    liquide.    Fr.    Liquid  glue. 

„    marine.  Fr.    Marine  glue. 

„    de  poisson.    Fr.    Fish  glue. 
Collodionage.   Fr.  \        '  .    .  . 
Collodioniren.    Ger.)  Collodionising. 

Collodion  ricine.    Fr.    Enamel  collodion. 

„       sensibilise.    Fr.    Sensitive  collodion. 
Collodium.    Ger.  Collodion. 

„       verfahren,  trockenes.    Ger.    Collodio-bromide  process. 

„  „        nasses.    Ger.    Wet  collodion  process. 

Collodiumwolle.    Ger.\  p 
Colloxylin.    Ger.       J      *  J 
Colophane.    Fr      j  Resin 
Colophonmm.    Ger.  J 

Combinationsdruck.    Ger.    Combination  printing. 
Compensateur.    Fr.    Yellow  screen. 
Compositbild.    Ger.    Composite  portrait. 
Concentrirt.    Ger.    Saturated  (solution). 
Condensateur.    Fr.  Condenser. 
Contactdruck.    Ger.    Contact  print. 
Contretype.    Fr.    Reversed  negative. 
Controlluhr.    Ger.    Indicator,  register. 
Copie.    Ger.  Print. 

Copirautomat.    Ger.    Automatic  printing  machine. 

„    camera.    Ger.    Copying  camera. 

Copiren.    Ger.  Printing. 

Copirrahmen.    Ger.    Printing  frame. 

Corallin  gelbes.    Ger  A  . 

,,.     .  ^    r  Aunne. 

Corellme  jaune.    Fr.  J 

Corindon.    Fr.  Emery. 

Corps  de  la  monture.    Fr.    Lens  tube. 

Coton  azotique.    Fr.\  „  .. 

^  I  Pyroxylin. 

„     poudre.    Fr.  J 

Couche  sensible.    Fr.    Sensitive  film. 

Coupe  ovale.    Fr.    Print  trimmer. 

Courbure  de  champ.    Fr.    Curvature  of  field. 

Coussin  de  feutre.    Fr.    Felt  pads. 

Couvercle  de  l'objectiv.   Fr.    Lens  cap. 

Crayeuse  epreuve.    Fr.    Chalky  print. 

Cremaillere.    Fr.    Rack  and  pinion. 

Creuset.    Fr.  Crucible. 

Cristalline.    Fr.  Aniline. 

606 


IV.  SYNONYMS. 


Crochet.    Fr.  Dipper. 
Crocus.    Gey.    Oxide  of  iron. 
Cyankalium.    Gey.    Potassium  cyanide. 

Cyanofer.   Fr  j  Cyanotype. 

Cyanotypverfahren.  Ger) 
Cyanure.    Fr.  Cyanide. 

Cyanwasserstoffseife.    Ger.    Potassium  cyanide  soap. 

D 

Daguerrotypie.    Fy.  Daguerrotype. 
Dammar harz.    Gey.    Gum  Dammar. 
Dauerpapier.   Gey.    Ready  sensitised  paper. 
Deckung.    Gey.  Density. 

Definition  sur  les  bords.    Fy.    Marginal  definition. 
Degradateur.    Fy.  Vignette. 
Deltapapier.    Gey.    Gelatino-chloride  paper. 
Demiteintes.    Fy.  Half-tones. 

Depot  pulverulent  blanc.    Fy.    White  powdery  deposit  (lime). 

Destilliren.    Gey.    To  distil. 

Deutoxyde  de  mercure.  Fy.  Mercuric  oxide. 

Dialyse.   Fy.  Dialysis. 

Diaphanaskop.    Gey.   Diaphanoscope,  lanternoscope. 
Diaphragme  centrale.    Fy.    Central  diaphragm. 

„         etoile.    Fy.    Star  stop. 

,  Iris.    Fr.    Iris  diaphragm. 

„        qui  reduit  l'lntensite*  lumineuse  du  ciel.  Fr,  Cloud  stop. 

„         tournant.    Fy.    Wheel  diaphragm. 
Diapositiv.    Gey.  Transparency. 
Diazodruck.    Gey.    Diazotypc  printing. 
Dichtigkeit.   Ger.  Density. 
Distance  focale.    Fy.  Focus. 
Doigtier.   Fr.   Plate  lifter. 
Doppelcassette.   Gey.    Double  dark  slide. 

Doppelgangerbild.    Ger.     Double  photograph,  one  person  in  two 

positions  on  one  plate. 
Doppeljodid.    Gey.    Solution  of  silver  iodide  in  potassium  iodide. 
Doppelobjectiv.    Gey.    Doublet  lens. 

Doppeltchromsiiures  Ammoniak.    Ger.   Ammonium  bichromate. 

„  Kali.    Gey.    Potassium  bichromate. 

Doppeltkohlensaures  Natron.    Gey.    Sodium  bicarbonate. 
Doppeltransportverfahren.    Ger.   Double-transfer  carbon  pro©  ss, 
Dosenlibelle.   Gey.  A  level. 
Double  tirage.    Fr.   Combination  printing. 

607 


APP.ENp.IX. 


Draussenaufnahme.    Ger.   Outdoor  photography. 
Drehblende.    Ger.    Revolving  or  wheel  diaphragm. 
Dreibeinstativ.   Ger.  Tripod  stand. 
Drillingscassette.    Ger.   Multiple  dark  slide. 
Druck.    Ger.  Print. 
Drucken.    Ger.  Printing. 
Dunkelzelt.    Ger.    Dark  tent. 

„     zimmer.    Ger.   Dark  room. 

,,         „      larape.    Ger.   Dark  room  lamp. 

Durcir.   Fr.   To  harden. 

Dynaktinometer.   Ger.  \  . 

„       Y  Actinometer. 
„       metre.  Fr.  J 

E. 

Eau  brom.ee.   Fr.   Bromine  water. 

„    chloree.   Fr.    Chlorine  water. 

„    de  Javelle.   Fr.    Eau  de  Javelle. 

„    mere.   Fr.    Mother  liquor, 
regale.    Fr.   Aqua  regia. 
Ebenheit  des  Feldes.    Ger.   Flatness  of  field. 
Ebonit.    Ger.  Ebonite. 

Eburneumverfahren.   Ger.    Eburneum  process. 
Eclair  magnesique.   Fr.   Magnesium  flash  light. 
Eclairage.   Fr.  Lighting. 

„        a  la  Rembrandt.   Fr.   Rembrandt  lighting. 

, ,        inoffensif.   Fr.    Non-actinic  light. 
Ecran  d'eclairage.    Fr.  Reflector, 
jaune.    Fr.   Yellow  screen. 
„      strie.   Fr.   Cross-line  screen. 
Ecrou  du  pied.    Fr.   Tripod  head. 
Effets  du  jour  et  du  nuit.   Fr.   Dissolving  views. 
Einfaches  objectiv.    Ger.   Single  landscape  lens. 
Einfachtransportverfahren.    Ger.   Single-transfer  carbon  process. 
Einfallswinkel.    Ger.   Angle  of  incidence. 
Eingebrannte  Photographien.    Ger.   Ceramic  photographs. 
Einlage.    Ger.   Printing-frame  pad. 
Einlagen.    Ger.   Carriers  for  dark  slides. 
Einstaubverfahren.    Ger.   Powder  process. 
Einstellen.   Ger.  To  focus. 
Einstell-loupe.    Ger.    Focussing  magnifier. 
Einstellschraube.    Ger.   Focussing  screw. 
Einstelltuch.    Ger.    Focussing  cloth. 
Eintaucher.    Ger.  Dipper. 

608 


IV.  SYNONYMS. 


Eisenblaudruck.    Ger.   Cyanotype  process. 
Eisenchlorid.    Ger.   Ferric  chloride. 
Eisenflecken.    Ger.    Particles  of  iron. 
Eisenoxalat.    Ger.    Ferric  oxalate. 

„     oxyde.    Ger.   Ferric  oxide. 

„        ,,     schwefelsaures.    Ger.   Ferric  sulphate. 

„     vitriol.    Ger.   Ferrous  sulphate. 
Eisessig.    Ger.   Glacial  acetic  acid. 
Eiweiss.    Ger.  Albumen. 
Elemente.   Ger.  Elements. 
Elfenbeinschwarz.    Ger.    Ivory  black. 
Emailfarbe.    Ger.    Enamel  colours. 
Emailler.   Fr.   To  enamel. 

Emailphotographien.   Ger.        \     _  . 
_  ,  ?  ~       ]■    Ceramic  enamels. 

Emaux  photographiques.   Fr.  J 

Emeri.    Fr.  Emery. 

Empfindlichkeit.    Ger.  Sensitiveness. 

Emulsion  a  collodion  iodo-bromuree.   Fr.    Collodion  iodo-bromide 
emulsion. 

„        a  l'ebullition.   Fr.    Boiled  emulsion. 
Encre  de  Chine.  Fr.   Chinese  ink. 
Englisch  Roth.    Ger.   Oxide  of  iron. 
Entfarben.   Ger.   To  clear,  decolorise. 
Entwickelung.    Ger.  Development. 

„  sdruck.    Ger.    A  print  by  development,  e^g.  bro.nitle. 

Entwickler.    Ger.  Developer. 
Eosin-blaustich.    Ger.  Erythro.sin. 
Epreuve.    Fr.    Proof,  print. 
Epreuves  bombees.    Fr.    Cameo  prints. 

,,       sans  eclat.    Fr.    Flat  prints. 
Escamoter  les  plaques.    Fr.    To  change  plat(  5. 
Esprit  de  bois.    Fr.    Wood  spirit,  methylated  spirit. 
Essence  de  goudron.    Fr.    Coal-tar  oil. 

„      huile  terebinthine.    Fr.    Spirit  of  turpentin< 

„      de  poires.    Fr.    Amyl  acetate. 
Essigsaure.    Ger.    Acetic  acid. 
Essigsaureamylester.    Ger.    Amyl  acetate. 
Essigsaures  Blei.    Ger.    Lead  acetate 

,,         Eisenoxydul.    Ger.    Ferrous  acetate. 
„         Natron.    Ger.    Sodium  acetate. 
Essoreuse.    Fr.    Centrifugal  machine. 
Etendage.    Fr.    Coating  (plates). 
Etoffe  jaune.    Fr.    Canary  medium. 

609  R  K 

I 


APPENDIX. 


Euryskop.  Gcr.  Euryscopc. 
Exposition.    Ger.  Exposure. 

„        messer.    Ger.    Exposure  meter. 

F. 

Faiblisseur.    Fr.  Reducer. 

Fallverschluss.    Gcr.    Drop  shutter. 

Farbenempfindlich.    Ger.    Colour  sensitive. 

Farbschleier.    Ger.    Green  fog. 

Farrine  fossile.    Fr.    Infusorial  earth. 

Fecule.    Fr.  Starch. 

Federharz.    Ger.  India-rubber. 

Fernobjectiv.    Ger.    Telephotographic  lens. 

Ferreux,  sels  ferreux.    Fr.    Ferrous  salts. 

Ferricyanure  de  potassium.    Fr.    Ferricyanide  of  potassium. 

Ferridcyankalium.    Ger.    Ferridcyanide  of  potassium. 

Ferrioxalat.    Ger.    Ferric  oxalate. 

Ferriques,  sels  ferriques.    Ferric  salts. 

Ferroacetat.    Ger.    Ferric  acetate. 

Ferrotypie.    Fr.,  Ger.  Ferrotype. 

Ferrotyplack.    Ger.    Benzole  or  crystal  varnish. 

Fiel  de  boeuf.   Fr.  Ox-gall. 

Firniss.    Ger.  Varnish. 

Fischleim.    Ger.  Isindass. 

Fixage.    Fr.  Fixation. 

Fixirbad.    Ger.    Fixing  bath. 

„       saures.    Ger.    Acid  fixing  bath. 
Fixirnatron.    Ger.    Hyposulphite  of  soda. 
Flacon  comptes  gouttes.    Fr.    Drop  glass. 
Fleurs  de  zink.    Fr.    Oxide  of  zinc. 
Floue,  image  floue.    Fr.    Flat  image. 
Fluorwasserstoffsaure.    Ger.    Hydrofluoric  acid. 
Flussaure.    Ger.    Hydrofluoric  acid. 
Flussmittel.    Ger.  Flux.- 

Focale,  distance  focale.    Fr.    Focus,  focal  length. 

Focimetre.    Fr.  Focimeter. 

Focus-differenz.    Ger.    Non-coincidence  of  foci. 

„    messer.    Ger.  Focimeter. 

„    tiefe.    Ger.    Depth  of  focus. 

„    weite.    Ger.    Focus,  focal  length. 
Folien.    Ger.  Films. 
Fond.    Fr.  Background. 
Foyer    Fr.  Focus. 

610 


IV.  SYNONYMS. 


Freilichtaufnahmen.    Ger.    Outdoor  photography. 
Fulmi-coton.    Fr.  Pyroxylin. 
Fumigation.    Fr.  Fuming. 

G. 

Gaiacol.    Ger.  Guaiacol. 

Gallussaure.    Ger.    Gallic  acid. 

Ganze  Platte.    Ger.    Wholeplate,  8.V  x  61  inches. 

Gasgluhlicht.    Ger.    Incandescent  gas  light. 

Gaze  azote.    Fr.  Nitrogen. 

„    nitreux.    Fr.    Nitrous  oxide. 
Geheimcamera.    Ger.    Detective  camera. 
Gelatine  bichromatee.    Fr.    Bichromated  gelatine. 
Gelatinobromure.    Fr.  Gelatino-bromide. 
Gelatinochlorure.    Fr.  Gelatino-chloride. 
Gelatinotypie.    Fr.  Leimtype. 
Gelbfarbung.    Ger.    Yellow  stain. 

,,   scheibe.    Ger.    Yellow  screen. 

„   schleier.    Ger.    Yellow  stain. 

„   wurzel.    Ger.  Turmeric. 
Gerben.    Ger.    To  harden. 
Gerbsaure.    Ger.    Tannic  acid. 
Gesicbtsfeld.    Ger.      \  . 

Gesichts-winkel.    Ger.)  An&lc  of  v,ew'  angle  mcluded  by  lenb' 

Giessen.    Ger.    To  coat. 

Gla^age.    Far.  Enamelling. 

Glaserkitt.    Ger.  Putty. 

Glashaus.    Ger.  Studio. 

Glimmer.    Ger.  Mica. 

Glu  marine.    Fr.    Marine  glue. 

Goldbad.    Ger.    Gold  bath,  toning  bath. 

Goldchloridkalium.    Ger.    Chloride  of  gold  and  potassium. 

Goldgelber  Stoff.    Ger.    Canary  medium. 

Goldsalz.    Ger.    Gold  salt. 

Goldsaures  Ammoniak.    Ger.    Fulminating  gold. 
Gomme.    Fr.  Gum. 

„      elastique.    Fr.  India-rubber. 

„      laque.    Fr.  Shellac. 
Gommeline.    Fr.  Dextrin. 
Gravimcter.    Fr.  Hydrometer. 
Gravure  heliographique  sur  zinc.    Fr.    Zinc  etching. 

„  „  en  taille  douce.    Fr.  Photogravure. 

Gnines  Plattenputzpulver.    Ger.    Infusorial  earth. 

6n 


APPENDIX. 


Griinschleier.    Ger.    Green  fog. 
Guajakharz.    Ger.    Guaiacum  resin. 
Guillotineverschluss.    Ger.    Drop  shutter. 
Gummi.    Ger.  Gum. 

„      elasticum.    Ger.  India-rubber. 

„      lack.    Ger.  Shellac. 

„      Quetschwalze.    Ger.    Roller  squeegee.  ' 

H. 

Halo.    Fr.  Halation. 

Harten.    Ger.    To  harden. 

Harzseife.    Ger.    Resin  soap. 

Hausenblaes.    Ger.  Isinglass. 

Haute.    Ger.  Films. 

Heiss-satinir  maschine.    Ger.  Burnisher. 

Heliogravure.    Ger.  Photogravure. 

Hermetischer  Verschluss.    Ger.    Hermetically  sealing. 

Hervorrufung.    Ger.  Development. 

Hintergrund.    Ger.  Background. 

Hinterkleiden.    Ger.  Backing. 

Hirschhornsalz.    Ger.    Ammonium  carbonate. 

Hof.    Ger.  Halation. 

Hone  lichter.    Ger.    High  lights. 

Hbllenstein.    Ger.    Silver  nitrate. 

Holzalkohol.    Ger.    Methylated  spirit. 

Holzessig — Holzessigsaure.    Ger.    Pyroligneous  acid. 

Holzgeist.    Ger.    Methylated  alcohol. 

Honig.    Ger.  Honey. 

Hornsilber.    Ger.    Silver  chloride. 

Huile  de  lavande.    Fr.    Oil  of  lavender. 

„        lin.    Fr.    Linseed  oil. 
Hydrogene.    Fr.  Hydrogen. 

„        sulfure.    Fr.    Sulphuretted  hydrogen. 
Hydrooxygenlicht.    Ger.    Oxy-hydrogen  light. 
Hydrothionsaure.    Ger.    Sulphuretted  hydrogen. 
Hydrure  de  phenyle.    Fr.  Benzine. 
Hyposulfite  de  soude.    Fr.    Hyposulphite  of  soda 

I. 

Iconogene.    Fr.  Eikonogen. 

Iconometre.   Fr.  \  ,7. 

_     }  View  meter. 
Ikonometer.  Ger.) 

Image  confuse.    Fr.    Flat  image. 

612 


IV.  SYNONYMS. 


Image  double.    Fr.    Double  image. 
Impression  par  contact.    Fr.    Contact  printing. 
Infusorienerde.    Ger.    Infusorial  earth. 
Innenaufnahmen.    Ger.  Interiors. 
Instantanes.    Fr.    Instantaneous  shots. 
Intensite.    Fr.    Intensity,  density. 
Interieurs.    Fr.  Interiors. 
Inter  mediaires.    Fr.  Carriers, 
lode.    Fr.  Iodine. 
Iodure.    Fr.  Iodide. 
Irisblende.    Ger.    Iris  diaphragm . 
Islandisches  Moos.    Ger.    Iceland  Moss. 
Ivoire  vegetal.    Fr.    Vegetable  ivory. 

J. 

Jalousiecassette.    Ger.    Roller-blind  dark  slide 
Jalousieverschluss.    Ger.   Blind  shutter. 
Javelle'sche  Lauge.    Ger.    Eau  de  Javellc. 
Jenenser  Glas.    Ger.    Jena  glass. 
Jod.    Ger.  Iodine. 

Jodammonium.    Ger.    Ammonium  iodide. 

Jodbromsilber-Collodium  emulsion.     Ger.    Iodo-bromide  collodion 
emulsion. 

Jodbromsilber-Gelatine  emulsion.      Ger.      Iodo-bromide  gelatine 
emulsion. 

Jodcadmium.    Ger.    Cadmium  iodide. 

calcium.    Ger.    Calcium  iodide. 
„  collodium.    Ger.    Iodised  collodion. 
„  eosin.    Ger.  Erythrosin. 
„  kalium.    Ger.    Potassium  iodide. 
„  lithium.    Ger.    Lithium  iodide. 

natrium.    Ger.    Sodium  iodide. 

papier.    Ger.    Iodised  paper. 
„  quecksilber.    Ger.    Mercuric  iodide. 
„  tinctur.    Ger.    Iodine  tincture. 

wasserstoff.    Ger.    Hydriodic  acid. 
„  zink.    Ger.    Zinc  iodide. 

K. 

Kali  Blausaures.    Ger.    Potassium  cyanide. 
Kaliumchromalaun.    Ger.    Chrome  alum. 

„     eisencyanid.    Ger.    Ferridcyanide  of  potassium. 

„        „    cyanur.    Ger.    Ferrocyanide  of  potassium. 

6x3 


APPENDIX. 


Kaliumnatriumtartrat.    Ger.    Rochelle  salts. 

„     platinchlortir.    Ger.    Chloroplatinite  of  potassium. 

,,     wasserglas.    Ger.    Silicate  of  potassium. 
Kalk.    Ger.  Chalk. 

„   gebrannter.    Ger.  Quick-lime. 

„   geloschter.    Ger.    Slaked  lime. 
Kalklicht.    Ger.  Limelight. 

Kalkschleier.    Ger.    White  powdery  deposit  (lime). 

Kaltemischungen.    Ger.    Freezing  mixtures. 

Kappenrohr.    Ger.    Flange,  lens  hood. 

Kasein.    Ger.  Casein. 

Kautschuk.    Ger.  India-rubber. 

Keragyre.    Fr.    Silver  chloride. 

Kienruss.    Ger.  Lampblack. 

Kieselguhr,  geschlammter.    Ger.    Infusorial  earth. 
Kieselsauresalze.    Ger.  Silicates. 
Kieselsaures  Kali.    Ger.    Silicate  of  potash. 
Kippschalen.    Ger.    Well  dish. 
Kitt.    Ger.  Putty. 
Klammern.    Ger.  Clips. 

Klappenverschluss.    Ger.    Flap  shutter,  sky  shade  shutter. 

Klarbad.    Ger.    Clearing  bath. 

Klarheit.    Ger.  Clearness. 

Kleben.    Ger.  Mounting. 

Kleesaure.    Ger.    Oxalic  acid. 

Kleister.    Ger.    Starch  paste. 

Knallgas.    Ger.  Hydrogen. 

Kochemulsion.    Ger.    Boiled  emulsion. 

Kochsalz.    Ger.    Common  salt. 

Koliledruck.    Ger.    Carbon  printing. 

Kohlendisulfid.    Ger.    Carbon  bisulphide. 

Kohlensaure.    Ger.  Carbonate. 

Konigswasser.    Ger.    Aqua  regia. 

Kopf  halter.    Ger.    Head  rest. 

Kopfscbirm.    Ger.  Reflector. 

Korn.    Ger.  Grain. 

Kraft.    Ger.  Density. 

Kraftigung.    Ger.  Intensification. 

Krauseln.    Ger.  Frilling. 

Kreidiges  Bild.    Ger.    Chalky  print. 

Kreosot.    Ger.  Creasote. 

Kronglas.    Ger.    Crown  glass. 

Krummung.    Ger.  Curvature. 

614 


IV.  SYNONYMS. 


Kugelobjectiv.    Ger.    Globe  lens. 
Kupfer.    Ger.  Copper. 

„     vitriol.    Ger.    Sulphate  of  copper. 

L. 

Laboratoire  noire.    Fr.    Dark  room. 

Lack.    Ger.  Varnish. 

Lackmus.    Ger.  Litmus. 

Lampe  de  laboratoire.    Fr.    Dark  room  lamp. 

Lampenruss.    Ger.  Lampblack. 

landschaftslinse.    Ger.    Landscape  lens. 

Lanterne  americaine.    Fr.    Sciopticon  lantern. 

„       magique.    Fr.    Magic  lantern. 
Lapis.    Ger.    Silver  nitrate. 
Laque.    Fr.  Shellac. 
Latentes  Bild.    Ger.    Latent  image. 
Laterna  magica.    Ger.    Magic  lantern. 
Laternbilder.    Ger.    Lantern  slide. 
Laufbrett.    Ger.  Baseboard. 
Lavendelbl.    Ger.    Oil  oflavender. 
Ledercollodium.    Ger.    Enamel  collodion. 
Leimtypie.    Ger.  Leimtype. 
Leinol.    Ger.    Linseed  oil. 
Lentille.    Fr.  Lens. 
Leucbtfarbe.    Ger.    Luminous  paint. 
Leveur  des  plaques.    Fr.    Plate  lifter. 
Libelle.    Ger.  Level. 
Lichen  d'Islande.    Fr.    Iceland  moss. 
Lichtbildmesskunst.    Ger.  Photogrammetrv. 
Lichtdruck.    Ger.  Collotype. 
Lichtempfindlichkeit.    Ger.  Sensitiveness. 
Lichter,  hone.    Ger.    High  lights. 
Lichtfleck,  centraler.    Ger.    Flare  spot. 
Lichthof.    Ger.  Halation. 

Lichtkraft  eines  objectiv.    Ger.    Rapidity  of  a  lens. 
Lichtkupferdruck.    Ger.  Photogravure. 
Lichtpapier.    Ger.    Waxed  tissue  paper. 
Lichtpausverfahren.    Ger.  Cyanotypc. 
Lichtschleier.    Ger.    Light  fog. 
Lignin.    Ger.  Cellulose. 
Lineaturen.    Ger.    Screen  plates. 
Linotypie.    Ger.    Enlargements  on  canvas. 
Linse.    Ger.  Lens. 

61.S 


APPENDIX. 


Locale  Verstarkung.    Ger.    Local  intensification. 
Lochcamera.    Ger.    Pinhole  camera. 
Longuer  de  foyer.    Fr.    Focal  length. 
Losung.    Ger.  Solution. 

Loupe  de  mis  au  point.    Fr.    Focussing  magnifier. 

„     redressante.    Fr.    Erecting  eyepiece. 
Lourde,  epreuves  lourdes.    Fr.    Flat  prints. 
Luftblasen.    Ger.    Air  bells. 
Luftperspektiv.    Ger.    Aerial  perspective. 
Lumiere  diffuse.    Fr.    Diffused  light. 

„      de  Drummond.    Fr.  Limelight. 

„      eclair.    Fr.  Flashlight. 
Lumieres,  grandes  lumieres.    Fr.    Lights,  high  lights. 
Lut  de  vitrifier.    Fr.  Putty. 

M. 

Macgilp.    Ger.  Maglip. 
Magazin.    Ger.  Magazine. 

Magnesie  noire.    Fr.    Black  oxide  of  manganese. 
Magnesiumblitzlicht.    Ger  A  _„  . 

„        putzlicht.    Ger.)  Magnes>"m  flashlight. 
Magnium.    Ger.  Magnesium. 

Makrophotographie.    Ger.    Macrophotography,  enlarging. 

Mangane.    Fr.    Black  oxide  of  manganese. 

Mangansuperoxyde.    Ger.    Black  oxide  of  manganese. 

Marienbad.    Ger.    Hot-water  bath. 

Marienglas.    Ger.  Mica. 

Marineleim.    Ger.    Marine  glue. 

Marquer  automatique.    Fr.    Automatic  indicator. 

Marques.    Fr.  Spots. 

Masken.    Ger.  Masks. 

Masquer.    Fr.    To  back  (plates). 

Mastix.    Ger.  Mastic. 

Matrize.    Ger.  Negative. 

Mattlack.    Ger.    Matt  varnish. 

Mattolein.    Ger.    Matt  varnish  (Dammar  I  part,  turpentine  5  parts). 

Mattscheibe.    Ger.    Ground  glass,  focussing  screen. 

Maturation.    Fr.  Ripening. 

Megilp.  Ger\ 

Megilpe.  Fr.) 

Mehlig.    Ger.  Mealy. 

Menisque.    Fr.  Meniscus. 

Mennige.    Ger.    Minium,  red  lead. 

616 


IV.  SYNONYMS. 


Mensur.    Ger.    Graduated  measure. 
Mercure.    Fr.  Mercury. 
Mercurographie.    Ger.    Merc  urography. 
Mere  lessive.    Fr.    Mother  liquor. 
Messbildverfahren.    Ger.  Photogrammetry. 
Metadiphenol.    Fr.  Resorcin. 
Metallflecken.    Ger.    Metallic  spots. 
Methylalkohol.    Ger.    Methylated  spirit. 
Miel.    Fr.  Honey. 

Mikrophotographie.    Ger.  Microphotography. 

Milch.    Ger.  Milk. 

Milchglas.    Ger.    Opal  glass. 

Milchsaure.    Ger.    Lactic  acid. 

Milchsaures  Silber.    Ger.    Lactate  of  silver. 

Minium.    Fr.    Red  lead. 

Mise  au  point.    Fr.  Focussing. 

Modell.    Ger.  Sitter. 

Molken.    Ger.  Whey. 

Momentaufnahmen.    Ger.    Instantaneous  exposures. 

„     verschluss.    Ger.    Instantaneous  shutter. 
Mondscheineffect.    Ger.    Moonlight  effect. 
Monochrom.    Ger.  Monochrome. 
Monosulfure  de  potassium.    Fr.    Liver  of  sulphur. 
Mortier.    Fr.  Mortar. 
Moscouade.    Fr.    Cane  sugar. 
Muscovit.    Ger.  Mica. 
Mutterlauge.    Ger.    Mother  liquor. 

N. 

Nadelstiche.    Ger.  Pinholes. 
Natrium.    Ger.  Sodium. 

weinstein.    Ger.    Tartrate  of  soda  and  potash. 
Naturalphotographie.    Ger.    Naturalistic  photography. 
Nebelbild.    Ger.    Dissolving  view. 
Negatif  de  dessins  au  trait.    Fr.    Line  negative. 

„      sur  papier.    Fr.    Paper  negative. 
Negativ.    Ger.  Negative. 

bad.    Ger.    Negative  bath. 
„      lack.    Ger.    Negative  varnish. 
ft     papier.    Ger.    Negative  paper. 

retoucbe.    Ger.    Negative  retouching. 
„      stander.    Ger.    Drying  rack. 
„     waschkasten.    Ger.    Plate  washer. 

6i7 


APPENDIX. 


Peinture  de  Balmain.    Fr.    Luminous  paint. 
Pellicules.    Fr.  Films. 

„        a  celluloides.    Fr.    Celluloid  films. 

„        d'huilage.    Fr.    Negative  paper. 
Perdre  de  l'intensite.    Fr.    To  lose  depth,  intensity,  vigour. 
Perlsalz.    Ger.    Sodium  phosphate. 
Petrole.    Fr.  Naphtha. 
Phenylamin.    Ger.\  AnUine 
Phenylamine.  Fr.) 
Phenylsaure.  Ger.    Carbolic  acid. 
Phosphin.    Ger.  Chrysanilin. 
Phosphor.    GerA  ph  horus. 
Phosphore.  Fr.) 

Phosphorographie.    Ger.  Phosphorography. 
Phosphorsaures  Natron.    Ger.    Sodium  phosphate. 

„  Silber.    Ger.    Silver  phosphate. 

Photochemigraphie.    Ger.    Zinc  etching  in  line. 
Photochromie.    Ger.  Crystoleum  painting. 
Photocopie.    Fr.  Positive,  print. 
Photogalvanographie.    Ger.  Photo-galvanography. 
Photoglyptie.    Ger.    Woodbury-type  printing. 
Photogrammetrie.    Ger.    Surveying  by  photography. 
Photographie  ohne  Objectiv.    Ger.    Pinhole  photography. 

„         stereoscopique.    Fr.    Stereoscopic  photography. 

,,  sur  bois.    Fr.    Photography  on  wood. 

„         vitrifiees.    Fr.  Enamels. 
Photogravure  directe.    Fr.    Line  and  half-tone  block-making. 

„  du  mercure.    Fr.  Mercurography. 

,,  sur  zinc.    Fr.  Zincography. 

Photolithophane.    Ger.    Photography  on  porcelain. 
Photo  livre.    Fr.    Book  camera. 
Photomecanique.    Fr.  Photo-mechanical. 
Photomechanische  verfahren.  Ger.    Photo-mechanical  process. 
Photometre.    Ft.  Photometer. 
Photominiatiir.    Ger.    Crystoleum  painting. 
Photoplastigraphie.    Ger.  Photo-sculpture. 
Photorelief.    Ger.  Woodbury-type. 
Photosculptur.    Ger.  Photo-sculpture. 

Phototel.    Ger.  ~\    A  process  of  transmitting  photos  along  a 

Phototelegraphie.    Fr.  j        wire  by  electricity. 
Phototopographie.    Ger.    Photographic  surveying. 
Phototype.    Fr.  Negative. 

Phototypogravure.    Fr.    Line  and  half-tone  block-making. 

6i8 


IV.  SYNONYMS. 


Orthoskopisches  Objectiv.    Ger.    Orthoscopic  lens. 
Optische  Brennpunkt.    Ger.    Visual  focus. 

„       Sensibilisatoren.    Gey.    Optical  sensitisers. 
Ouverture  de  l'objectif.    Fr.    Lens  aperture. 
Oxalsaure.    Ger.    Oxalic  acid. 
Oxalsaures  Eisenoxyd.    Ger.    Ferric  oxalate. 

„         Ammon.    Ger.    Ammonio-ferric  oxalate. 

„  Natron.    Ger.    Sodio-ferric  oxalate. 

„        Eisenoxydul.    Ger.    Ferrous  oxalate. 
Oxalsaures  Kali  neutrales.    Ger.    Neutral  oxalate  of  potash. 

„        Natron.    Ger.    Sodium  oxalate. 

„        Silber.    Ger.    Silver  oxalate. 
Oxaniline.    Fr.  Paramidophenol. 
Oxyammoniaque.    Fr.    Hydroxylamin  hydrochlorate. 
Oxydes.    Fr.  Oxides. 
Oxygene.    Fr.  Oxygen. 
Oxyphenol.    Fr.  Pyrocatechin. 
Ozon.    Ger.  Ozone. 


P. 

Panier  laveur.    Fr.    Plate  washer. 
Panoramalinse.    Ger.    Panoramic  lens. 
Papier  albumine.    Fr.    Albumenised  paper. 

„  „        brillant.    Fr.    Double  albumenised  paper. 

„      couche.    Fr.    Baryta  paper. 

dioptique.    Fr.    Waxed  tissue  paper. 
„     au  gelatino-chlorure.    Fr.    Gclatino-chloride  paper. 

„  bromure.    Fr.    Gelatino-bromide  paper. 

„     iodnree.    Fr.    Iodised  paper. 
„     n^gatif.    Fr.  \ 
„     negativ.    Ger.)  Negatlve  paper- 
„     nitroglucose.    Fr.    Nitro-glucose  paper. 

photographique.    Fr.    Photographic  plain  paper. 
„     positif  pelliculaire.    Fr.    Transferotype  paper. 

reactif.    Fr.    Test  paper. 
,,      sale.    Fr.    Plain  salted  paper. 

de  Saxe.    Fr.    Saxe  paper. 
„      sensible  albumine.    Fr.    Ready  sensitised  paper. 
„      similiplatine.    Fr.    Simili-platine  paper. 
Papyrographie.    Ger.,  Fr.  Papyrography. 
Parasoleil.    Fr.    Lens  hood. 
Patronen.    Ger.  Cartridge. 

619 


APPENDIX. 


Neige,  battre  en  neige.    Fr.    Snow,  to  beat  to  snow. 

Nettete.    Fr.    Sharpness  (of  image). 

Netznegativ.    Ger.    Line  screen. 

Nicol'sches  Prisma.    Ger.    Nicol's  prism. 

Nitramidin.    Ger.  Xyloidine. 

Nitrirterzucker.    Ger.  Nitro-glucose. 

Nitroglucosepapier.    Ger.    Nitro-glucose  paper. 

Nitrostarke.    Ger.  Xyloidine. 

Niveau  d'air,  niveau  a  bulles  d'air.    Fr.  Level. 

Nivellirgestell.    Ger.  Level. 

Noir  animal.    Fr.    Ivory  black. 

„    de  fumee.    Fr.  Lampblack. 

„    d'ivoire.    Fr.    Ivory  black. 

;,   de  platine.    Fr.    Platinum  black. 

O. 

Objectif.    Fr.    Objective,  lens. 

„      achromatique.    Fr.    Achromatic  lens. 
„       double.    Fr.    Doublet  lens. 


„      a  portraits.    Fr.    Portrait  lens. 

rectilineare  grand  angle.    Fr.    Wide-angle  rectilinear. 
„      simple.    Fr.    Single  lens. 
„      symetrique.    Fr.    Symmetrical  lens. 
„      telephotographique.    Fr.    Telephotographic  lens. 
Objectiv.    Ger.    Objective,  lens. 
„      brett.    Ger.    Lens  board. 
„      deckel.    Ger.    Lens  cap. 


„      satz.    Ger.    Casket  lens. 
„      verschluss.    Ger.    Instantaneous  shutter. 
Obturateur.    Fr.  Shutter. 


Oeffnung  der  linse  or  des  Objectivs.  Ger.  Lens  aperture. 
Oel.    Ger.  Oil. 

Opalplatten.    Ger.    Opal  plates. 
Oppositions.    Fr.  Contrasts. 


Ochsengalle.    Ger.  Ox-gall. 


a  clapet.    Fr.    Flap  shutter, 
a  guillotine.    Fr.    Drop  shutter, 
a  rideau.    Fr.    Blind  shutter, 
a  secteurs.    Fr.    Sector  shutter. 


620 


IV.  SYNONYMS. 


Randscharfe.    Ger.    Marginal  definition. 

Rasterplatte.    Ger.    Ruled  or  line  screen. 

Rauchern.    Ger.    To  fume. 

Reagenspapier.    Ger.    Test  paper. 

Recolte  des  residus.    Fr.    Recovery  of  residues. 

Rectilinearlinse.    Ger.    Rectilinear  lens. 

Reducteur.    Fr.  Reducer. 

Reductionsmittel.    Ger.  Reducers. 

Reflecteur.    Fr.  Reflector. 

Reflectorschirm.    Ger.  Reflector. 

Reibschale.    Ger.  Mortar. 

Reifen.    Ger.    To  ripen. 

Reisecamera.    Ger.    Tourist  camera. 

Reisestativ.    Ger.    Tourist  stand. 

Reliefdruck.    Ger.    Woodbury-type  printing. 

Rembrandtbeleuchtung.    Ger.    Rembrandt  lighting. 

Renforcateur.    Fr.  Intensifier. 


a  l'azotate  de  plomb.    Fr.    Lead  intensifier. 
a  l'azotate  d'urane.    Fr.    Uranium  intensifier. 
au  mercure.    Fr.    Mercury  intensifier. 


Residus.    Fr.  Residues. 
Resine  de  dammar.    Fr.    Gum  Dammar. 

„         ga'iac.    Fr.    Gum  Guaiacum. 
Retardateur.    Fr.  Restrainer. 
Retouche.    Fr.  Retouching. 
Retouchirlack.    Ger.    Retouching  medium. 
Retouchirpult.    Ger.    Retouching  desk. 
Revelateur.    Fr.  Developer. 
Revolveblende.    Ger.    Wheel  diaphragms. 
Rhodanammonium.    Ger.    Ammonium  sulphocyariide. 
Rhodankalium.    Ger.    Potassium  sulphocyanidc. 
Rochellesalz.    Ger.    Rochelle  salts. 
Rohcollodium.    Ger.    Plain  collodion. 
Rohpapier.    Ger.    Plain  paper. 
Rbhrenlibelle.    Ger.  Level. 
Rohrzucker.    Ger.    Cane  sugar. 
Rollcassette.    Ger.    Roll  holder. 
Rosolsaure.    Ger.  Aurine. 
Rotationsapparat.    Ger.    Panoramic  camera, 
Rotheisenstein.    Ger.  V  _  . . 


Renforcement.    Fr.  Intensification. 


Rdthel.    Ger.  /  ^xme 

Rothschleier.    Ger.    Red  log. 


621 


APPENDIX. 


Rouge  de  quinoleine.  Fr.  Chinoline  red. 
Rouleau  a  collage.  Fr.  Roller  squeegee. 
Riickstande.    Ger.  Residues. 

Russische  bilder.    Ger.    Vignettes  on  black  ground. 


Sac  a  escamoter.    Fr.    Changing  bag. 
Safran  des  Indes.    Fr.  Turmeric. 
Salmiak.    Gen  Sal-ammoniac. 
Salon  de  pose.    Fr.  Studio. 
Saloncamera.    Ger.    Studio  camera. 
Salpeter.  Ger.\ 

e  .  a.         7-     r  Potassium  nitrate. 
Salpetre.    Fr.  J 

Salpetergas.    Ger.  Nitrogen. 

Salpetersalzsaure.    Ger.    Aqua  regia. 

Salpetersaure.    Ger.    Nitric  acid. 

Salpetersaures  Ammoniak.    Ger.    Ammonium  nitrate. 

„  Blei.    Ger.    Lead  nitrate. 

„  Eisenoxydul.    Ger.    Ferrous  nitrate. 

Uranoxyd.    Ger.    Ferric  nitrate. 

„  Uranoxydul.    Ger.    Uranium  nitrate. 

Salpetrigesaure.    Ger.    Nitrous  acid. 

Salpetrigsaures  Kali.  Ger.    Potassium  nitrite. 

Salzpapier.    Ger.    Plain  salted  paper. 

Salzsaure.    Ger.    Hydrochloric  acid. 

Salzs'aures  Blei.    Ger.    Lead  chloride. 

Hydroxylamin.    Ger.    Hydroxylamin  hydrochloride. 

Sammellinse.    Ger.    Convergent  or  positive  lens. 

Sandarak.    Ger.  \ 

_     ,  „   v  Sandarac. 

Sandaraque.    Fr.  f 

Sandbad.    Ger.    Sand  bath. 

Saponite.    Fr.    Talc,  French  chalk. 

Satinage.    Fr.  Burnishing. 

Satiniren.    Ger.    To  burnish. 

Sauerstoff.    Ger.  Oxygen. 

Sauren.    Ger.  Acids. 

Saures  scbwefligsaures  Kali.    Ger.    Potassium  metabisulphite. 

„  „  Natron.    Ger.    Acid  sulphite  of  soda, 

i         weinsaures  Kali.    Ger.    Cream  of  tartar. 
Savon  a  l'acide  cyanhydrique.    Fr.    Cyanide  soap. 
Schalen.    Ger.  Dishes. 
Scharfe.    Ger.    Definition,  sharpness. 
Schatten.    Ger.  Shadows. 

622 


IV.  SYNONYMS. 


Pkotoxylographie.    Ger.    Photography  on  wood  blocks. 
Photozinkographie.    Ger.  Photozincography. 
Physikalische  Entwickelung.    Ger.    Physical  development. 
Pied.    Fr.  Stand. 

„     d'atelier.    Fr.    Studio  stand. 

„    canne.    Fr.    Walking-stick  stand. 

,,    parapluie.    Fr.    Umbrella  stand. 

"    table.    Fr.    Studio  or  table  stand. 
Pierre  infernale.    Fr.    Silver  nitrate. 

„     ponce.    Fr.    Pumice  stone. 
Pince  a  cliches.    Fr.    Plate  lifter. 
Pinces  americaines.    Fr.    American  wooden  clips. 
Planchette  d'objectif.    Fr.   Lens  board. 

„         se  deplacant  dans  les  deux  sens.   Fr.  Shifting 
lens  board. 

Planitude  des  champs.   Fr.   Flatness  of  field. 
Plaque  entiere.   Fr.   Whole  plate. 

„      souple.   Fr.  Films. 
Platindruck.    Ger.   Platinotype  process. 
Platine.   Fr.  Platinum. 

Platinkaliumchlonir.   Ger.   Chloroplatinite  of  potash. 

Platinmohr.    Ger.    Platinum  black. 

Platinpapier.    Ger.  Platinotype  paper. 

Platinschwarz.    Ger.    Platinum  black. 

Platten.   Ger.  Plates. 

Plattentrockenstander.    Ger.    Drying  rack. 

Plattenformate.    Ger.   Plate  sizes. 

Plattenhalter  pneumatischer.    Ger.   Pneumatic  holder. 

Plattenheber.   Ger.   Plate  lifter. 

Plattenwaschkasten.   Ger.   Plate-washing  tank. 

Plattenwechselvorrichtung.   Ger.    Plate-changing  arrangement. 

Plattenzahler.    Ger.  Indicator. 

Plein  air.   Fr.   Open  air. 

Plissement.   Fr.  Frilling. 

Point  de  rosee.   Fr.   Dew  point. 

Porcelaine  transparente.   Fr.   Opal  glass. 

Porte-objectiv.   Fr.   Lens  board. 

„     plaques.   Fr.   Plate  sheaths. 
Portrait  a  l'interieur.   Fr.   Indoor  portraiture. 

„     en  plein  air.   Fr.   Outdoor  portraiture. 
Portrataufnabme.    Ger.  Portraiture. 
Portratbust.    Ger.   Bust  portrait. 
Portratobjectiv.    Ger.   Portrait  lens. 

623 


APPENDIX. 


Pose.  Fr.  \  „ 

_  ,      „     Y  Exposure. 

Pose,  temps  de.  Fr.  J 

,,    insuffisante.    Fr.    Insufficient,  under-exposure. 

Positif.   Fr.  Positive. 

„     pour  projection.    Fr.  Lantern  slide. 

„     sur  verre.   Fr.  Transparency. 
Positiv.   Ger.  Positive. 

Positivlack.    Ger.    Positive  varnish,  crystal  varnish. 

Positivpapier.   Ger.   Raw  paper. 

Positivretouche.   Ger.  Retouching  prints. 

Potasche,  *  Ger.    Potassium  carbonate. 

Poudrage,  procede  par.   Fr.   Powder  process. 

Poudre-coton.   Fr.  Pyroxylin. 

Poudre  d'email.   Fr.   Enamel  powder. 

Praservativ.   Ger.    1  ~ 

_  ,  >  Preservative. 

Preservateur.  Fr.  J 

Pressbausch.    Ger.   Felt  printing-frame  pad. 
Presse  a  satiner.   Fr.   Rolling  machine. 

„         „       a  chaud.   Fr.    Burnishing  machine. 
Primulinverfahren.   Ger.   Primuline  process. 
Prisma.    Ger.  Prism. 
Procede  au  charbon.   Fr.   Carbon  process. 

,,      du  double  transfert.  Fr.   Double-transfer  carbon 
Profondeur  de  foyer.  Fr.  Depth  of  focus. 
Projectionsapparat.   Ger.  Optical  lantern. 
Pupitre  a  retoucher.  Fr.   Retouching  desk. 
Pyrogall.  Fr.  \ 
Pyrogallol.   Ger.  I  Pyrogallic  acid. 

Pyrogallussaure.   Ger.  ) 
Pyrophotographie.    Ger.  Enamels. 
Pyroxyle.   Fr.  Pyroxylin. 


Q. 

Quart  de  plaque.   Fr.   Quarter  plate. 
Quecksilber.   Ger.  Mercury. 
Quecksilberchlorid.    Ger.   Mercuric  chloride. 
Quecksilberchloriir.   Ger.  Mercurous  chloride. 
Quecksilberjodid.    Ger.    Mercuric  iodide. 
Quecksilberverstarker.   Ger.   Mercury  intensifier. 
Quetscher.    Ger.  Squeegee. 

R. 

Raclette.    Fr.  Squeegee. 

624 


IV.  SYNONYMS. 


Schaukelcuvette.    Ger.    Automatic  rocker. 
Scheidewasser.    Ger.    Nitric  acid. 
Schellack.    Ger.  Shellac. 
Schichtseite.    Ger.    Film  side. 
Schiessbaumwolle.    Ger.  Pyroxylin. 
Schirmstativ.    Ger.    Umbrella  stand. 
Schlammkreide.    Ger.  Whitening. 
Schleier.    Ger.  Fog. 

Schlippe'sches  Salz.    Ger.    Schlippe's  salt. 
Schlitten.    Ger.  Baseboard. 
Schmelzfarben.    Ger.    Enamel  colours. 
Schmelzfarbenbilder.    Ger.  Enamels. 
Schmelztiegel.    Ger.  Crucible. 
Schnee.    Ger.  Snow. 

Schnellphotographie  Amerikanische.    Gcr.  Ferrotype. 
Schraffurplatten.    Ger.    Line  screen. 
Schwarzen  tiefste.    Ger.    Deepest  shadows. 
Schwefel.    Ger.  Sulphur. 

Schwefelammonium.    Ger.    Ammonium  sulphydrate. 
Schwefelantimon.    Ger.    Antimony  sulphide. 
Schwefelantimon-Schwefelnatron.    Ger.    Schlippe's  salt. 
Schwefelather.    Ger.    Sulphuric  ether. 

Schwefelcyanammonium.    Ger.    Ammonium  sulphocyanide. 
Scbwefelcyankalium.    Ger.    Potassium  sulphocyanide. 
Schwefelkohlenstoff.    Ger.    Carbon  disulphide. 
Schwefelleber.    Gcr.    Liver  of  sulphur. 
Schwefelmilch.    Ger.    Milk  of  sulphur. 
Schwefelsaure.    Ger.    Sulphuric  acid. 
Schwefelsaures  Eisenoxydul.    Ger.    Ferrous  sulphate. 

»>  ii        ammon.   Ger.   Ammonio-sulphate  of  iron. 

Schwefelsaures  Kupfer.    Ger.  \ 

,,      oxyd.    Gcr.  f  CoPPer  sulPhate. 
Schwefelsilber.    Ger.    Silver  sulphide. 
Schwefeltonung.    Ger.    Sulphur  toning. 
Schwefelwasserstoff.    Gcr.    Sulphuretted  hydrogen. 
Schwefelwasserstoff-Ammoniak.    Gcr.    Ammonium  sulphydrate. 
Schweflige  Saure.    Gcr.    Sulphurous  acid. 
Schwefligsaures  Natron.    Gcr.    Sodium  sulphite. 
Schwimmwaage.    Ger.  Hydrometer. 
Sectorenverschluss.    Ger.    Sector  shutter. 
Seignettesalz.    Ger.    Rochelle  salts. 
Sel.    Fr.  Salt. 

„    Ammonia  .    Fr.  Sal-ammoniac. 

625  S  S 


APPENDIX. 


Sel  de  cuisine.    Fr.    Common  salt. 
„  Saturne.    Fr.    Sugar  of  lead. 
„  Schlippe.    Fr.    Schlippe's  salt. 
„    „  Seignette.    Fr.    Rochelle  salts. 
Selen.    Ger.  Selenium. 

Selle's  Uranverstarker.    Ger.    Selle's  uranium  intensifier. 
Sensibilisatoren,  chemischer.    Ger.    Chemical  sensitisers. 
Sensibilisiren.    Ger.    To  sensitise. 
Sensibilite.    Fr.  Sensitiveness. 
Sensitocolorimeter.    Ger.    Colour  sensitometer. 
Sicherheitsrand.    Ger.    Safe  edge. 
Silber.    Ger.  Silver. 

Silberalbuminat.    Ger.    Silver  albuminate. 
Silberbad.    Ger.    Silver  bath. 
Silberbromid.    Ger.    Silver  bromide. 
Silberchlorid.    Ger.    Silver  chloride. 
Silberchlorur.    Ger.    Silver  subchloride. 
Silberdruck.    Ger.    Silver  print. 
Silberglanz.    Ger.    Silver  sulphide  (native). 
Silberjodid.    Ger.    Silver  iodide. 
Silbermesser.    Ger.  Argentometer. 
Silbernitrat.    Ger.    Silver  nitrate. 
Silbernitrit.    Ger.    Silver  nitrite. 
Silberoxalat.   Ger.   Silver  oxalate. 
Silberoxyd.   Ger.   Silver  oxide. 
Silbersalpeter.    Ger.   Silver  nitrate. 
Silbersulfid.    Ger.    Silver  sulphide. 
Silbersulphat.   Ger.   Silver  sulphate. 
Silicate.   Fr.  Silicate. 

Similiplatinpapier.   Ger.    Simile-platine  paper. 

Smirgel.   Ger.  Emery. 

Soda.    Ger.    Sodium  carbonate. 

Solution  qui  se  conserve.  Fr.   Stock  solution. 

Soufflet.    Fr.  Bellows. 

Soufre.   Fr.  Sulphur. 

Soulevements.  Fr.  Blisters. 

Sousexposition.  Fr.  Over-exposure. 

Speckstein.   Ger.  Talc,  French  chalk. 

Spektralanalyse.    Ger.    Spectrum  analysis. 

Spektrum.   Ger.  Spectrum. 

Support  a  vis  calantes.   Fr.   Levelling  stand. 

Surexposition.    Fr.  Over-exposure. 


626 


IV.  SYNONYMS. 


T. 


Taches.   Fr.   Spots,  stains. 

„     metalliqu.es.   Fr.   Metallic  spots. 
Tafelglas.    Ger.    Ordinary  sheet  glass. 
Tamis  en  crin.   Fr.    Hair  sieve. 
Tanninverfahren.    Ger.    Tannin  process. 
Tassen.    Ger.  Dishes. 

Tauchcuvette.   Ger.   Dipping  bath  or  trough. 
Taucher.   Ger.  Dipper. 
Teinte.  Fr.  Tint. 

jaune.   Fr.   Yellow  stain. 
Teinteur  pour  positifs.    Fr.   The  cut-out  part  of  a  mask,  disc. 
Tele-objectiv.    Ger.  Telephotographic  lens. 
Temps  de  pose.  Fr.  Exposure. 
Tente.   Fr.   Dark  tent. 
Terpentinbl.    Ger.    Spirits  of  turpentine. 
Tetrabromfluorescein.    Ger.  Eosin. 


Thaupunkt.    Ger.    Dew  point. 

Thierische  substanzen.   Ger.  Animal  substances. 

Thierkohle.   Ger.   Animal  charcoal. 

Tiefe  des  focus.   Ger.  Depth  of  focus. 

Tintencopirverfahren.    Ger.    Ink  process. 

Tirage.    Fr.  Printing. 

Tischstativ.    Ger.    Studio  or  table  stand. 

Tonen.    Ger.  Toning. 

Tonfixirbad.    Ger.    Combined  toning  and  fixing  bath. 


patronen.    Ger.    Combined  toning  and  fixing  cartridges. 


Topophotographie.  Ger.  Photographic  surveying. 
Tournesol.    Fr.  Litmus. 


Trame  artificielle.    Fr.    Screen  plate,  line  screen. 
Transfert.    Fr.  Transfer. 
Transparentbild.    Ger.  Transparency. 
Traubenzucker.    Ger.  Glucose. 

Traumaticin.    Ger.    Solution  of  india-rubber  in  chloroform. 
Triebrohr.    Ger.    Lens  tube. 
Trockenplatten.    Ger.    Dry  plates. 
Trockenplattenlack.    Ger.    Dry-plate  varnish. 
Trockenschrank.    Ger.  Drying  cupboard. 
Trockenstander.    Ger.    Drying  rack. 
Tropfglas.    Ger.    Drop  glass. 


kalium.    Ger.  Erythrosin. 


Tragacanth. 


APPENDIX. 


Trous  d'epingle.    Fr.  Pinholes. 

„     d'objectif.    Fr.    Casket  lenses. 
Tusche.    Ger.    Indian  ink. 
Tuyau  mouture  de  l'objectif.    Fr.    Lens  tube. 
Typogravure.    Fr.    Process-block  making. 

U. 

Ueberbelichtung.    Ger A  Over-exposure. 
Ueberexposition.    Ger.  J 
Ueberfangglas.    Ger.    Flashed  glass. 

Uebermangansaures  Kali.    Ger.    Potassium  permanganate. 
Unschadlicb.es  Licht.    Ger.    Safe  light. 
Unterbelichtung.    Ger.  Under-exposure. 
Unterchlorigsaures  Calcium.    Ger.    Chloride  of  lime. 
Unterexposition.    Ger.  Under-exposure. 
Unterschwefligsaures  Goldoxydulnatron.    Ger.    Sel  d'or. 

„  Natron.    Ger.    Sodium  hyposulphite. 

Unze.    Ger.  Ounce. 

Uraneopirverfahren     Ger.    Uranium  printing  process. 
Uranglas.    Ger.    Uranium  glass. 
Urannitrat.    Ger,     )    Uranium  nitrate. 
Uranylnitrat.    Ger  J 

Uranverstarker.    Ger.    Uranium  intensifier. 


V. 

Ventouse  pneumatique.    Fr.    Pneumatic  ho 
Verbleichen.    Ger.    To  bleach. 

Verbranntes  Bild.    Ger.    Burnt  out,  over-exposed  picture. 
Vergilben.    Ger.    To  yellow,  to  turn  yellow. 
Vergrbssern.    Ger.    To  enlarge. 
Vergrosserungsapparat.    Ger.    Enlarging  apparatus. 
Vernis.    Fr.  Varnish. 

,,      depoli.    Fr.    Matt  varnish. 

,,     a  negatifs.    Fr.    Negative  varnish. 

„     siccatif.    Fr.  Meglip. 
Verre.    Fr.  Glass. 

„     depoli.    Fr.    Ground  glass. 

„     de  Muscovie.    Fr.  Mica. 

,,     d'urane.    Fr.    Uranium  glass. 
Verschluss.    Ger.    Shutter  (instantaneous). 
Verschwommenes  Bild.    Ger.    Fuzzy  image. 
Verstarker.    Ger.  Intensifier. 
Verstarkung.    Ger.  Intensification. 

628 


IV.  SYNONYMS. 


Verzeichnung.    Ger.  Distortion. 
Verzogerer.    Ger.  Restrainer. 
Viertelplatte.    Ger.    Quarter  plate. 
Vignetten.    Ger.  Vignettes. 
Vignettirdeckel.    Ger.    Vignetting  board. 
Vinaigre  de  bois.    Fr.    Pyroligneous  acid. 

glacial.    Fr.    Glacial  acetic  acid. 
Virage.    Fr.  Toning. 
Vis  de  rappel.    Fr.    Focussing  screw. 
Viseur.   Fr.  Finder. 
Visirscheibe.    Ger.    Focussing  screen. 
Visitkarte.    Ger.  Carte-de-visite. 
Vitriolsaure.    Ger.    Sulphuric  acid. 
Voile.    Fr.  Fog. 

„     jaune.    Fr.    Yellow  fog. 

„     noir.    Fr.    Black  fog. 

„     rouge.    Fr.    Red  fog. 

„     vert.    Fr.    Green  fog. 
Volet  a  coulisses  du  chassis.    Fr.    Shutter  of  dark  slide. 
Vorbad.    Ger.    Preliminary  bath. 
Vorderblende.    Ger.    Diaphragm  in  front  of  lens. 
Vorrathslbsung.    Ger.    Stock  solution. 

W. 

Wachs.  Ger. 

Waschkasten.    (*<  or  print  washer. 

Wasser.    Ger.  Wau 
Wasserfirniss.    Ger.    Water  varnish. 
Wasserfrei.    Ger.  Anhydrous. 
Wasserglas.    Ger.    Potassium  silicate. 
Wasserstoff.    Ger.  Hydrogen. 
Wasserstoffsuperoxyd.    Ger.    Hydrogen  peroxide. 
Wasserwaage.    Ger.    Water  level,  spirit  level. 
Wechselkasten.    Ger.    Changing  box. 
Wechseln  der  Platten.    Ger.    Changing  plates. 
Wechselsack.    Ger.    Changing  back. 
Weinsaure.    Ger.  \ 
Weinsteinsaure.    Ger  J  Tartaric  acid. 
Weinstein.    Ger.    Potassium  bitartrate. 
Weitwinkelobjectiv.    Ger.    Wide-angle  lens. 

Wiedergewinnung  des  gebrauchten  Silbers.     Ger.     Recovery  of 

silver  residues. 
Wblbung  des  Bildes.    Ger.    Curvature  of  the  field. 

629 


APPENDIX. 


Wolframsaures  Natron.    Ger.    Sodium  tungstate. 
Wolkenblende.    Ger.    Cloud  stop. 
Woodburydruck.    Ger,    Woodbury-type  printing. 

X. 

Xylo'idine.    Ger.,  Fr.  Xyloidine. 
Xylophotographie.    Ger.    Photography  on  wood. 

Z. 

Zahlvorrichtung.    Ger.    Indicator,  register. 
Zahnstangentrieb.    Ger.    Rack  and  pinion. 
Zaponlack.    Ger.    Varnish  of  pyroxylin  and  amyl  acetate. 
Zauberphotographien.    Ger.  •  Magic  photographs. 
Zeitaufnahmen.    Ger.    Time  exposure. 
Zelt.    Ger.  Tent. 

Zerstreutes  Licht.    Ger.    Diffused  light. 
Zerstreuunglinse.    Ger.    Negative  or  divergent  lens. 
Zimmeraufnahmen.    Ger.    Indoor  portraiture. 
Zink.    Ger.  Zinc. 

Zuckerkalk-entwickler.    Ger.    Calcium  saccharate  developer. 

Zuckersaure.    Ger.    Oxalic  acid. 

Zu  Schnee  schlagen.    Ger.    To  beat  to  a  froth. 

Zweifach  chromsaures  Kali.    Ger.    Potassium  bichromate. 


630 


£5 


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